Systems and methods for enhancing blood circulation

ABSTRACT

A method for increasing circulation in a breathing person utilizes a valve system that is interfaced to the person&#39;s airway and is configured to decrease or prevent respiratory gas flow to the person&#39;s lungs during at least a portion of an inhalation event. The person is permitted to inhale and exhale through the valve system. During inhalation, the valve system functions to produce a vacuum within the thorax to increase blood flow back to the right heart of the person, thereby increasing cardiac output and blood circulation.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation in part application of U.S.patent application Ser. No. 10/119,203, filed Apr. 8, 2002, which is acontinuation in part application of U.S. patent application Ser. No.09/854,238, filed May 11, 2001, which is a continuation in partapplication of U.S. patent application Ser. No. 09/546,252, filed Apr.10, 2000, which is a continuation of U.S. patent application Ser. No.08/950,702, filed Oct. 15, 1997 (now U.S. Pat. No. 6,062,219), which isa continuation-in-part application of U.S. patent application Ser. No.08/403,009, filed Mar. 10, 1995 (now U.S. Pat. No. 5,692,498), which isa continuation-in-part application of U.S. patent application Ser. No.08/149,204, filed Nov. 9, 1993 (now U.S. Pat. No. 5,551,420), thedisclosures of which are herein incorporated by reference.

[0002] This application is also related to U.S. application Ser. No.09/967029, filed Sep. 28, 2001, the complete disclosure of which isherein incorporated by reference.

BACKGROUND OF THE INVENTION

[0003] The present invention relates generally to devices and methodsused in conjunction with increasing blood circulation. In particular,the present invention relates to devices and methods for increasingblood circulation in spontaneously breathing individuals.

[0004] Many individuals have a need to increase their blood circulation.This can be the case even if the person is considered to have normalblood circulation. One obvious way to increase blood circulation is toparticipate in physical activity, such as running, walking, swimming andthe like. However, participation in such activities may be inconvenient,and in some cases unpractical or altogether impossible.

[0005] Hence, this invention is related to alternative techniques forincreasing blood circulation.

BRIEF SUMMARY OF THE INVENTION

[0006] In one embodiment, the invention provides a method for increasingcirculation in a breathing person. According to the method, a valvesystem is interfaced to the person's airway and is configured todecrease or prevent respiratory gas flow to the person's lungs during atleast a portion of an inhalation event. The person is permitted toinhale and exhale through the valve system. During inhalation, the valvesystem functions to produce a vacuum within the thorax to increase bloodflow back to the right heart of the person, thereby increasing cardiacoutput and blood circulation. More specifically, coupling of the valvesystem to a breathing person increases the magnitude and prolongs theduration of negative intrathoracic pressure in the person's chest, i.e.,increases the duration and degree that the intrathoracic pressure isbelow or negative with respect to the pressure in the peripheral venousvasculature to increase venous return. By enhancing the amount of venousblood flow into the heart and lungs (since equilibration ofintrathoracic pressure during inhalation occurs to a greater extent fromenhanced venous return rather than rapid inflow of gases into the chestvia the patient's airway) cardiopulmonary circulation is increased.

[0007] In one aspect, the valve system is incorporated into a facialmask that is coupled to the person's face. In another aspect, the valvesystem includes a pressure responsive inflow valve that may have anactuating pressure in the range from about 0 cm H₂O to about −40 cm H₂O.Conveniently, the actuating pressure of the valve may be varied overtime.

[0008] In one particular aspect, the valve system may also be configuredto prevent or decrease exhaled gases from exiting the person's lungsduring at least a portion of an exhalation event to further increaseblood circulation. To increase the circulation, the valve system may beinterfaced for a time period in the range from about 30 seconds to about24 hours. In a further aspect, a supply of oxygen may be added throughthe valve system to supplement oxygen delivery to the person. The valvesystem also functions to deliver this oxygen into the blood byincreasing circulation through the lungs, and also increasing tidalvolume (the amount of gas that enters the lungs with each breath).

[0009] Such a method may also be used to treat various diseases, such asdiseases that are related to impaired venous blood flow or from poorblood circulation. Examples of such conditions that may be treated usingsuch techniques include venous stasis ulcers, deep vein thrombosis,wound healing, and lymphedema. The invention may also be used to treatrenal failure.

[0010] In a specific embodiment, impeding the airflow into the patient'slungs is accomplished by the use of a flow restrictive or limitingmember, such as a flow restrictive orifice disposed within or connectedin series with a lumen of a ventilation tube, or a pressure-responsivevalve within a lumen of the tube to impede the inflow of air. Thepressure-responsive valve is biased to open to permit the inflow of airwhen the intrathoracic pressure falls below a threshold level. In orderto properly ventilate the patient, the method may permit the injectionof respiratory gases. When periodic ventilation is performed, gases canbe delivered either through the impeding step or in another embodimentthey can bypass the impeding step. In some cases, an oxygen enriched gasmay be supplied to the patient through the pressure-responsive valveonce this valve opens.

[0011] A specific embodiment further provides means for impeding airfrom leaving the lungs during exhalation to further enhancecardiopulmonary circulation by enhancing positive intrathoracicpressure.

[0012] An apparatus for enhancing cardiopulmonary circulation accordingto one embodiment may comprise an improved endotracheal tube having aflow restrictive element for impeding airflow from the patient's lungsduring chest inhalation. A second apparatus according to the inventionprovides for an improved air-delivery system comprising a compressiblestructure having a flow restrictive element included in or attached toan opening of the compressible structure to impede the flow of gases tothe patient's lungs. Also, a connector is provided for interfacing thecompressible structure to the patient, preferably by attaching a facialmask or endotracheal tube to the structure. Alternatively, a mouth piecemay be coupled to the valving system.

[0013] In another aspect of the invention, a valving system is providedfor regulating airflow into a patient's lungs when breathing. The systemincludes a housing having an upstream region and a downstream region. Ameans is provided between the upstream region and the downstream regionfor inhibiting air from flowing from the upstream region to thedownstream region when the pressure in the downstream region is lessthan the pressure in the upstream region. In this manner, air isinhibited from flowing into the patient's lungs during an inhalationattempt thereby forcing more venous blood into the chest and enhancingvital organ perfusion. A means is further provided for allowing air toflow into the downstream region when ventilating the patient. In thisway, adequate ventilation can be provided to the patient during theprocedure.

[0014] In one particular aspect, the inhibiting means comprises a valvewhich inhibits airflow from the upstream region to the downstream regionwhen the pressure in the downstream region is less than the pressure inthe upstream region. The valve preferably includes a diaphragm which isclosed when the pressure in the downstream region is less than or equalto the pressure in the upstream region. Such a configuration preventsair from flowing into the patient's lungs during an attempted inhalationwhile allowing air to be exhausted from the patient's lungs duringexhalation. Preferably, the diaphragm is constructed of a flexiblemembrane. Alternatively, the diaphragm can be constructed using a ball.

[0015] In another particular aspect, the diaphragm is biased to openwhen the pressure in the downstream region is about 2 cm H₂O or greater,and more preferably at about 2 cm H₂O to 10 cm H₂O. Biasing of thediaphragm in this manner increases intrathoracic pressure duringexhalation to further enhance vital organ perfusion.

[0016] In still a further aspect, the means for allowing air into thedownstream region includes a means for opening the diaphragm when air isinjected into the upstream region to ventilate the patient. The meansfor opening the diaphragm preferably includes an ambient pressure regionthat is adjacent the diaphragm. When air is injected into the upstreamregion, the pressure within the upstream region increases therebydrawing the diaphragm into the ambient pressure region and allowing theair to flow to the patient's lungs.

[0017] In an alternative aspect, the means for allowing air into thedownstream region comprises a pressure-responsive valve at thedownstream region. The pressure-responsive valve allows air into thedownstream region when the pressure in the downstream region falls belowa threshold level, usually in the range from 0 cm H₂O to −40 cm H₂O. Thepressure-responsive valve is advantageous in allowing ventilation to beprovided to the patient while still employing the diaphragm to enhancethe extent and duration of negative intrathoracic pressure. Examples ofpressure-responsive valves that may be used include, for example, aspring biased valve, an electromagnetically driven valve, or a valveconstructed of any deflectable material that will deflect when thethreshold pressure is exceeded. As one specific example, the valve maybe constructed of a magnetically charged piece of material with a narrowtolerance that is attracted to a gate. This valve will open when themagnetically charged gate pressure is exceeded. In this way, when thenegative intrathoracic pressure is exceeded, the valve will be pulledaway from the gate to permit gases to flow to the lungs. Such a valvecould also be used in place of the diaphragm valve discussed above.

[0018] In one option, a source of oxygen-enriched gas may be coupled tothe pressure-responsive valve to supply an oxygen-enriched gas to thepatient when the pressure-responsive valve is opened. A regulator may beemployed to regulate the pressure and/or flow rate of the gas. Forexample, the pressure may be regulated to be less than the actuatingpressure of the valve so that the pressurized gas will not flow to thepatient's lungs until the valve is opened when the negativeintrathoracic pressure is exceeded.

[0019] The system of the invention in another aspect is provided with anair exhaust opening in the housing at the upstream region for exhaustingair from the housing. A valve is provided in the exhaust opening whichinhibits air from flowing into the housing through the exhaust opening.In this manner, air exhausted from the patient is in turn exhausted fromthe housing through the exhaust opening. In a further aspect, means areprovided for preventing air from exiting the housing through the exhaustopening during injection of air into the housing when ventilating thepatient. Preferably air is injected into the housing from a respiratorydevice, such as a respiratory bag, a ventilator, or the like.

[0020] In still a further aspect of the invention, an endotracheal tube,a sealed facial mask, a laryngeal mask, or other airway tube,mouthpiece, or the like is provided and is connected to the housing atthe downstream region for attachment to the patient. The endotrachealtube or like device is for insertion into the patient's airway andprovides a convenient attachment for the valving system to the patient.

[0021] In one embodiment, the invention provides a mechanism to vary theactuating pressure of the inflow valve. In this way, a person is able tooperate the mechanism to vary the impedance. In some cases, the valvesystems of the invention may include a pressure gauge to display theintrathoracic pressures. By having this information readily available,the user has more information to assist in setting the desired actuatingpressure of the inflow valve.

[0022] In one aspect, the varying mechanism is configured to vary theactuating pressure to a pressure within the range from about 0 cm H₂O toabout −40 cm H₂O. In another aspect, the inflow valve comprises a shafthaving a seal that is configured to block an opening in the housing, anda spring that biases the seal against the housing. With such aconfiguration, the mechanism may comprise a knob that is movable to varythe biasing force of the spring. For example, the knob may be rotatablycoupled to the shaft so that the user may simply turn the knob to varythe actuating pressure.

[0023] In another embodiment, the valve systems of the invention may beprovided with a safety ventilation passage. If the valve system isinappropriately applied to a patient who is spontaneously breathing, thepatient may breathe through this passage while the valve system iscoupled to the patient's airway. A safety mechanism is used to maintainthe safety ventilation passageway open to permit respiratory gases tofreely flow to the patient's lungs until actuated by a rescuer to closethe safety ventilation passageway. With such an arrangement, the patientis able to freely breathe if they are capable of so doing.

[0024] In one aspect, the safety ventilation passageway is providedthrough the inflow valve when the inflow valve is in an open position.With this configuration, the safety mechanism is configured to maintainthe inflow valve in the open position until actuated by the user to movethe inflow valve to a closed position. A variety of ways may be used toactuate the safety mechanism. For example, the housing may include aventilation port to permit respiratory gases to be injected into thehousing, and the safety mechanism may comprise a sensor to sense whenthe rescuer injects respiratory gases into the housing. In oneembodiment, a signal from the sensor is used by a control system to movethe inflow valve from the open position to the closed position. As anexample, the sensor may be movable upon injection of respiratory gasesinto the housing, and the control system may comprise a set of gearsthat are coupled to the sensor and a cam that is movable by the gears toclose the inflow valve. Alternatively, the control system may comprisean electronic controller, a solenoid and a cam. This mechanism may beconfigured to take electrical signals from the sensor and to operate thesolenoid to move the cam and thereby close the inflow valve. As anotherexample, a flap may be moved upon injection of the gases. The flap maycause the movement of a variety of mechanical components that physicallyreset the inflow valve to the closed position.

[0025] A variety of sensors may be used to sense injection of therespiratory gases. For example, sensors that may be used includeelectronic switches that move in a gas stream, thermistors to sensetemperature changes, CO₂ detectors, materials that experience a changeof resistance when flexed, mechanical flaps that move in a gas stream,and the like.

[0026] The invention also provides methods for increasing the bloodpressure in a spontaneously breathing person. According to the method,an inflow valve is coupled to the person's airway and the person inhalesand exhales. During inhalation, the inflow valve inhibits or completelyprevents respiratory gases from entering the lungs for at least sometime to augment the person's negative intrathoracic pressure and therebyassist in increasing blood flow back to the right heart of the person.In so doing, the person's blood pressure is enhanced. The resistance oractuating pressure of the inflow valve may be based on one or moresensed physiological parameters. For example, one parameter may be thenegative intrathoracic pressure. For instance, the inflow valve may beused to achieve a negative intrathoracic pressure in the range fromabout 0 cm H₂O to −50 cm H₂O for flow rates in the range from about zeroflow to about 70 liters per minute. Other parameters that may be sensedinclude respiratory rate, end tidal CO₂, tissue CO₂ content, positiveend expiratory pressure, blood pressure and oxygen saturation. Theseparameters may be used individually or in combination when adjusting theresistance of the inflow valve. For example, even if the sensed negativeintrathoracic pressure is within a desired range, the end tidal CO₂ maybe outside of a desired range. As such, the resistance of the valve maybe adjusted until the end tidal CO₂ is acceptable. Conveniently, theinflow valve may be manually operated or operated in an automatedfashion. For example, a controller may be used to receive the sensedparameters and then to send signals to an adjustment mechanism thatoperates the valve to vary the resistance or actuating pressure.

[0027] Such a process may be used to treat a variety of conditions wherethe person's blood pressure is low. For example, such a procedure may beused where the person has low blood pressure due to blood loss, due tothe administration of a drug, due to a high gravitational state, due tovasodepressor syncope, due to drowning, due to heat stroke, due to heartattack, due to hypothermia, due to right heart failure, after a returnto earth from space, due to sepsis, pericardial effusion, cardiactamponade, or the like.

[0028] A further understanding of the nature and advantages of theinvention will become apparent by reference to the remaining portions ofthe specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a graph illustrating thoracic pressure changes over timewhen compressing and decompressing a patient's chest according to thepresent invention.

[0030]FIG. 2A is a schematic view illustrating airflow through aventilation circuit when compressing a patient's chest according to thepresent invention.

[0031]FIG. 2B is a schematic view illustrating airflow through aventilation circuit when decompressing a patient's chest according tothe present invention.

[0032]FIG. 3 is a schematic illustration of a first alternativeembodiment of a device for impeding airflow into a patient's lungsaccording to the present invention.

[0033]FIG. 4A is a schematic illustration of a second alternativeembodiment of the device for impeding airflow into a patient's lungsaccording to the present invention.

[0034]FIG. 4B is a schematic illustration of the device in FIG. 4A witha common inhalation/exhalation port.

[0035]FIG. 5A is a schematic view of a one-way valve used in the devicefor impeding airflow according to the present invention.

[0036]FIG. 5B is a schematic view of the one-way valve in FIG. 5A thatis held open.

[0037]FIG. 5C is a schematic view of a one-way valve that is closeduntil a threshold pressure is present in the tube according to thepresent invention.

[0038]FIG. 6A is a schematic view of a spring biased inflow valve and aspring biased expiration valve to be used in accordance with the presentinvention.

[0039]FIG. 6B is a schematic view of FIG. 6A showing the operation ofthe valves during outflow of air.

[0040]FIG. 6C is a schematic view of FIG. 6A showing the operation ofthe valves during inflow of air.

[0041]FIG. 7 is a schematic view of a single valve that is spring biasedfrom both sides to be used as an inflow valve and an expiration valveaccording to the present invention.

[0042]FIG. 8 is a schematic view of a flow restricting orifice to beused with a flow restrictive device according to the present invention.

[0043]FIG. 9 is a schematic view of an exemplary embodiment of thedevice for impeding airflow into a patient's lungs according to thepresent invention.

[0044] FIGS. 10A-10C are schematic views illustrating another embodimentof the present invention allowing for periodic patient ventilationthrough a bypassing valve.

[0045]FIG. 11 is a schematic view of an exemplary valving system forregulating airflow into a patient's lungs according to the presentinvention. The valving system is shown with air being exhausted from apatient's lungs.

[0046]FIG. 12 illustrates the valving system of FIG. 11 duringdecompression or resting of the patient's chest.

[0047]FIG. 13 illustrates the valving system of FIG. 11 with apressure-responsive valve being opened when the negative intrathoracicpressure in the patient's chest exceeds a threshold amount duringdecompression of the patient's chest.

[0048]FIG. 14 illustrates the valving system of FIG. 11 with a diaphragmbeing opened during injection of air into the housing when ventilatingthe patient.

[0049]FIG. 15 illustrates the valving system of FIG. 11 with a manuallyoperable valve being opened to allow air into the patient's lungs uponreturn of spontaneous circulation.

[0050]FIG. 16A is a cutaway side view of exemplary valving systemaccording to the present invention.

[0051]FIG. 16B is a top view of a deflector and a fenestrated mount ofthe valving system of FIG. 16A.

[0052]FIG. 16C is an alternative embodiment of the valving system ofFIG. 16A.

[0053]FIG. 16D illustrates the valving system of FIG. 16A with a sourceof pressurized gas coupled to a pressure-responsive valve according tothe invention.

[0054]FIG. 17 is a schematic view of an alternative embodiment of avalving system having a ball as a diaphragm.

[0055]FIG. 18 is a schematic view of a device for impeding air flow intothe patient's lungs and for providing air to the patient's lungs whenneeded for ventilation.

[0056]FIG. 19 is a side view of one embodiment of a valving systemhaving an adjustable pressure responsive valve according to theinvention.

[0057]FIG. 20 is a cross sectional side view of the adjustable pressureresponsive valve of FIG. 19.

[0058]FIG. 21 is a top view of the valve of FIG. 20.

[0059]FIG. 22 illustrates the valve of FIG. 21 with a cap being removed.

[0060]FIG. 23 is a schematic side view of a safety mechanism for avalving system that permits respiratory gases to freely flow to thepatient's lungs through a ventilation passage according to theinvention.

[0061]FIG. 24 illustrates the safety mechanism of FIG. 23 when actuatedto prevent respiratory gases from flowing through the ventilationpassage.

[0062]FIG. 25 is a schematic side view of a valving system having anintegrated safety mechanism that permits respiratory gases to freelyflow to the patient's lungs through an inflow valve according to theinvention.

[0063]FIG. 26 illustrates a flow sensor and lever arm of the safetymechanism of FIG. 25 prior to actuation by the rescuer.

[0064]FIG. 27 illustrates the valving system of FIG. 25 when the safetymechanism is actuated by the rescuer to closed the inflow valve.

[0065]FIG. 28 illustrates the flow sensor and lever arm of FIG. 26 whenactuated by the rescuer.

[0066]FIG. 29 is an end view of the valving system of FIG. 25.

[0067]FIG. 30 is a more detailed view of the inflow valve of FIG. 25when in the open position.

[0068]FIG. 31 illustrates the inflow valve of FIG. 30 when in the closedposition.

[0069]FIG. 32 is a side schematic view of one embodiment of a safetyvalve shown in a closed position according to the invention.

[0070]FIG. 33 illustrates the safety valve of FIG. 32 in an openposition.

[0071]FIG. 34 is a side schematic view of another embodiment of a safetyvalve shown in a closed position according to the invention.

[0072]FIG. 35 illustrates the safety valve of FIG. 34 in an openposition.

[0073]FIG. 36 is a side schematic view of yet another embodiment of asafety valve shown in a closed position according to the invention.

[0074]FIG. 37 illustrates the safety valve of FIG. 36 in an openposition.

[0075]FIG. 38 is a schematic side view of an embodiment of a valvingsystem having a safety valve that is in a closed position according tothe invention.

[0076]FIG. 39 illustrates the valving system of FIG. 38 when the safetyvalve is moved to the open position during a gasp by a patient.

[0077]FIG. 40 illustrates the valving system of FIG. 38 duringventilation which causes the safety valve to move back to the closedposition.

[0078]FIG. 41 is a schematic diagram of a valving system having apressure gauge to measure pressures within the valving system accordingto the invention.

[0079]FIG. 42 is a cross-sectional schematic view of one embodiment of asystem for treating a breathing person who is in shock according to theinvention.

[0080]FIG. 43 is top schematic view of the system of FIG. 42.

[0081]FIG. 44 illustrates the system of FIG. 42 when the person isinspiring.

[0082]FIG. 45 illustrates the system of FIG. 42 when the person isexhaling.

[0083]FIG. 46A illustrates one embodiment of an inflow valve accordingto the invention.

[0084]FIG. 46B illustrates the inflow valve of FIG. 46A when theresistance to flow has been increased.

[0085]FIG. 47A illustrates another embodiment of an inflow valveaccording to the invention.

[0086]FIG. 47B illustrates the inflow valve of FIG. 47A when a disk hasbeen moved to increase flow resistance according to the invention.

[0087]FIG. 48A illustrates yet another embodiment of an inflow valveaccording to the invention.

[0088]FIG. 48B illustrates the inflow valve of FIG. 48A when a disk hasbeen rotated to increase resistance according to the invention.

[0089]FIG. 49A illustrates a further embodiment of an inflow valveaccording to the invention.

[0090]FIG. 49B illustrates the inflow valve of FIG. 49A when compressedto increase flow resistance.

[0091]FIG. 50A illustrates yet another embodiment of an inflow valveaccording to the invention.

[0092]FIG. 50B illustrates the inflow valve of FIG. 50A when compressedto increase flow resistance.

[0093]FIG. 51A illustrates a further embodiment of an inflow valveaccording to the invention.

[0094]FIG. 51B illustrates the inflow value of FIG. 51A when compressedto increase flow resistance.

[0095]FIG. 52A illustrates still a further embodiment of an inflow valveaccording to the invention.

[0096]FIG. 52B illustrates iris mechanisms that have been operated toincrease the resistance to flow of the inflow valve of FIG. 52A.

[0097]FIG. 53A illustrates still a further embodiment of an inflow valveaccording to the invention.

[0098]FIG. 53B illustrates the inflow valve of FIG. 53A when a disk hasbeen pivoted to increase flow resistance.

[0099]FIGS. 54A through 54C illustrate one embodiment of a method fortreating shock according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0100] According to the present invention, methods and devices forincreasing cardiopulmonary circulation induced by spontaneous breathingare provided. In particular, the invention improves blood circulation byproviding methods and devices which impede airflow into a patient'slungs to enhance negative intrathoracic pressure during attemptedinhalations, thus increasing the degree and duration of a pressuredifferential between the thorax (including the heart and lungs) and theperipheral venous vasculature. Enhancing negative intrathoracic pressurewith simultaneous impedance of movement of gases into the airway thusenhances venous blood flow into the heart and lungs and increasescardiopulmonary circulation.

[0101] In a broad sense, the present invention provides for occluding apatient's airway to prevent foreign (outside) air from flowing to apatient's lungs during attempted inhalations to enhance and sustain theduration of negative intrathoracic pressure and enhance bloodoxygenation and cardiopulmonary circulation. The patient's airway may beoccluded or inflow of gases impeded by any suitable device or mechanismsuch as by an endotracheal tube, a device attached to an endotrachealtube, a facial mask, a mouth piece used in mouth-to-mouth resuscitation,oropharyngeal airway, laryngeal mask airway, and the like.

[0102] A further aspect of the present invention provides for allowingimpeded air to flow into the patient's lungs during at least a portionof the inhalation attempt in order to provide some ventilation to thepatient while still enhancing the extent and duration of negativeintrathoracic pressure to enhance blood oxygenation. Impeding airflow tothe patient's lungs may be accomplished by any flow restrictive elementsuch as an orifice, a one-way valve, a spring biased or other valvewhich is set to open when the negative intrathoracic pressure is in therange from about 0 cm H₂O to −100 cm H₂O, and more preferably from about−3 cm H₂O to about −40 cm H₂O. A valve designed to open at a thresholdpressure value may be either fixed or variable, i.e., the pressure atwhich the valve opens may be adjusted or may be permanently fixed.Further, examples of pressure-responsive valves that may be usedinclude, for example, an electromagnetically driven valve or a valveconstructed of any deflectable material that will deflect when thethreshold pressure is exceeded. As one specific example, the valve maybe constructed of a magnetically charged piece of material with a narrowtolerance that is attracted to a gate. This valve will open, i.e.separate from the gate, when the magnetically charged gate pressure isexceeded. In this way, when the negative intrathoracic pressure isexceeded, the valve will be pulled away from the gate to permit gases toflow to the lungs.

[0103] In some cases, a safety mechanism may be provided to permitrespiratory gases to freely flow to the patient's lungs until the safetymechanism is actuated by the user. In this way, the valving system maybe coupled to the patient but will only impede patient inspiration untilactuated by the user.

[0104] Another aspect of the invention provides for air to be impededfrom leaving the patient's lungs during exhalation to further enhancecardiopulmonary circulation by enhancing intrathoracic pressure.Typically, air is impeded from leaving the lungs during the exhalationwhen the positive intrathoracic pressure is in the range from about 2 cmH₂O to 50 cm H₂O, and more preferably from about 2 cm H₂O to about 20 cmH₂O. Valves that may be used to accomplish such a feature include, forexample, a spring valve, a diaphragm valve, include diaphragmsconstructed of silicone, and a magnetically charged plate that iscoupled to a gate. In this manner, when the positive pressure exceedsthe magnetic force, the plate is forced away from the gate to permit thegases to exit the lungs.

[0105] Another aspect of the present invention provides for ventilatingor supplying a gas to the patient. Ventilation of the patient in oneembodiment is performed at about every two to 20 inhalation andexhalation cycles, preferably twice every fifteen cycles, thus providingsufficient fresh air or other gases for adequate gas exchange with theblood in the lungs to the patient. Ventilating the patient may beaccomplished by any device or method suitable such as by a compressibleor collapsible structure, by a ventilatory bag such as the AMBU bagavailable from AMBU, Copenhagen, Denmark, or the like. Ventilation couldalso be superimposed on the exhalation phase to further augment positiveintrathoracic pressure. Furthermore, periodic ventilation could beperformed either through the impeding step or by bypassing the impedingstep altogether.

[0106] In an alternative embodiment, ventilation may be provided byintroducing oxygen-enriched respiratory gases through thepressure-responsive valve that permits gases into the lungs during theinhalation step once a certain threshold negative intrathoracic pressureis exceeded. This could be introduced under pressure or at atmosphericpressure In this way, during each inhalation, respiratory gases may besupplied to the lungs to ventilate the patient. Use of a pressurized gasis advantageous in that more respiratory gases may be supplied to thelungs once the pressure responsive valve opens. The pressurized gas maybe supplied by connecting a pressurized gas source, such as apressurized tank or bag of O₂, to the back side of thepressure-responsive valve using a length of tubing. Conveniently, aregulator may be positioned between the pressure source and the valve toregulate the pressure and/or flow rate of the gas supplied from thepressure source. The pressure may be regulated such that it is less thanthe actuating pressure of the valve, e.g. by about 1 to 3 cm H₂O, sothat the valve will not prematurely open. For example, if respiratorygases are to be supplied to the patient when the negative intrathoracicpressure exceeds −14 cm H₂O, the pressure of the gas from the gas sourcemust be set to less than 14 cm H₂O.

[0107] One advantage of supplying supplemental oxygen through the valveand into the respiratory circuit is that addition of the supplementaloxygen may more efficiently be placed into the blood stream. This isbecause the valve helps to increase blood circulation through the lungsto facilitate the incorporation of additional oxygen into the lungs.Moreover, by injecting oxygen into the lungs, the tidal volume isincreased so that additional oxygen may be fed into the blood stream. Inone particular embodiment, such a configuration may be incorporated intoa diving mask so that a diver may incorporate more oxygen into the bloodwith a limited amount of oxygen (i.e., a tank of oxygen). Hence, theavailable oxygen may be better utilized, with less waste with eachbreath.

[0108] When ventilating a patient, the valves of the invention may bemodified to regulate the flow rate of air into the lungs. This may beaccomplished for example, by including a flow regulator, valve,restriction, reduced size orifice or the like within or associated withthe valve so that as respiratory gases are injected into the valve,their flow rate is limited below a threshold amount as the gases enterthe patient's airway. By regulating the flow rate of injectedrespiratory gases, the pressure on the esophagus may be kept withincertain limits to prevent gastronomic distention. For example, a reducedsize orifice may be provided at or near the exit opening of the valvesystem housing to regulate the gas flow rate before the gases enter thepatient's airway. In this way, a technique is provided to ensure thatsubstantially all of the injected respiratory gases enter the patient'slungs.

[0109] One significant advantage of the invention is the ability toincrease a person's blood pressure. By interfacing the valving systemsof the invention with spontaneously breathing patients, the valvingsystems are able to increase the negative intrathoracic pressure whenthe person inhales. By so doing, more blood is returned to the rightheart, thereby increasing the person's blood pressure. The valvingsystems used to increase the person's blood pressure may initiallycompletely prevent gas flow to the lungs during an inspiratory effort,or provide some measure of resistance. The complete prevention orinitial resistance may be adjusted sometime during the breathingmaneuver so that gas flow may proceed to the person's lungs for at leasta portion of the inspiratory cycle. For example, if using a pressureresponsive valve, the valve may be set to open when reaching a pressurein the range from about 0 cm H₂O to about −50 cm H₂O, more preferablyfrom about 0 cm H₂O to about −20 cm H₂O, and most preferably from about−5 cm H₂O to about −15 cm H₂O for flow rates of about zero flow to about70 liters per minute. For valves that simply provide resistance, thevalve may be configured to provide similar resistances during theinspiratory effort. Further, one or more sensors may be used to sensevarious physiological parameters and may be used to manually orautomatically vary the cracking pressure of the valve or the amount ofresistance produced by the valve.

[0110] Examples of situations where the valving systems of the inventionmay be used to increase blood pressure include those where aspontaneously breathing patient has experienced blood loss, or afterreceiving a drug (including an anesthetic agent) that causes a decreasein blood pressure. Patients with low blood pressure often suffer frominsufficient blood returning to the heart after each beat. This resultsin a decrease in forward blood flow out of the heart and eventually tolow blood pressure. By interfacing the valving systems to the airway,the amount of venous return to the right heart is increased to increaseblood pressure. Another example is where a spontaneously breathingpatient is in shock secondary to profound blood loss and needs increasedblood flow to the right heart. As a further example, such techniques maybe used with pilots or astronauts to increase blood flow back to theright heart in high gravitational states or when returning to earthafter space flight, and in patients who suffer from a rapid decrease inblood pressure due to vasovagal or vasodepressor syncope. Furtherexamples include low blood pressure due to heat stroke, drowning, heartattack, right heart failure, sepsis, pericardial effusion, tamponade, orthe like.

[0111] The valving systems of the invention may also incorporate or beassociated with sensors that are used to detect changes in intrathoracicpressures or other physiological parameters. Any of the sensorsdescribed herein may be configured to wirelessly transmit their measuredsignals to a remote receiver that is in communication with a controller.In turn the controller may use the measured signals to vary operation ofthe valve systems described herein. For example, sensors may be used tosense blood pressure, pressures within the heart, or the like and towirelessly transmit this information to a receiver. This information maythen be used by a controller to control the actuating pressure or theresistance of an inflow valve, to control the actuating pressure orresistance of an expiratory valve, to control the injection of oxygen orother gases, to control the administration of drugs or medications, orthe like.

[0112] The valve systems and/or facial masks of the invention may alsoinclude one or more ports for the administration of drugs or othermedicaments to the patient's respiratory system. For example, ports maybe provided for injecting medicaments by a syringe or pressurizedcanister. As another example, a nebulized liquid medicament may besupplied through such a port. As a further example, a powderedmedicament may be supplied through such a port.

[0113] Another feature of the invention is that it may be used todecrease intracranial pressures that often result from trauma to thehead. By decreasing intrathoracic pressures using the valve systems andtechniques of the invention, the resistance of venous return from thebrain to the heart is decreased. As such, more venous blood may beremoved from the brain, thereby decreasing intracranial pressures. Forexample, any of the valve systems of the invention may be coupled to thepatient's airway so that as the patient breathes, the negativeintrathoracic pressures generated by the patient are augmented to drawvenous blood out of the brain.

[0114] Referring now to FIG. 1, a graph illustrating thoracic pressurechanges over time when compressing and decompressing the patient's chestis shown. Area 10 represents the amount of thoracic pressure during thecompression phase of active compression-decompression CPR (ACD-CPR).Cross-hatched area 12 represents the negative thoracic pressure duringthe decompression step of ACD-CPR without a flow restrictive means torestrict the flow of air into the patient's lungs. Double cross-hatchedarea 14 represents the increase in negative thoracic pressure when thepatient's airway is occluded according to the present invention duringthe decompression step of ACD-CPR. The significance of the increase innegative intrathoracic pressure during the decompression step is thatmore venous blood is forced into the chest from the peripheral venousvasculature. Consequently, more blood is allowed to be oxygenated andmore blood is forced out of the chest during the next compression. Asimilar scenario is provided when the person is spontaneously breathingand the airway is occluded.

[0115] In the embodiments that follow, various devices, systems andmethods are described for enhancing the negative intrathoracic pressurein order to increase circulation. Although primarily described in thecontext of CPR, it will be appreciated that such devices, systems andtechniques may also be used for individuals that are spontaneouslybreathing and do not require the performance of CPR. Such individualsmay or may not be suffering from any specific type of disease orailment, but simply have a need for increased blood circulation (evenwith individuals having normal blood circulation). However, suchtechniques may be used for various diseases or ailments associated withblood circulation. For example, the invention may be used in casesrelated to impaired venous blood flow, such as venous stasis ulcers,deep vein thrombosis, wound healing, and lymphedema. Another example ismild/moderate renal failure.

[0116] Hence, the invention may function as a patent powered pump thatis capable of enhancing venous return and increasing cardiac output innormal patents and well as those suffering from diseases. In embodimentsdescribed in connection with CPR (such as when the chest is compressedand decompressed), it will be appreciated that exhalation and inhalation(respectively) are analogous steps for spontaneously breathingindividuals. For convenience of discussion, some embodiments will onlybe described in connection with CPR, with the understanding that suchembodiments may also be used in connection with spontaneously breathingsubjects as well. Further, other types of valve systems may also be usedto increase blood circulation in breathing subjects, such as thosedescribed in copending U.S. application Ser. No. 09/966945, filed Sep.28, 2001; and Ser. No. 09/967029, filed Sep. 28, 2001, the completedisclosures of which are herein incorporated by reference.

[0117] In an exemplary embodiment, airflow may be impeded to thepatient's lungs during inhalation by placing a ventilatory mask over thepatient's mouth and nose. The ventilatory mask also has apressure-responsive valve attached to prevent airflow to the patient'slungs until the negative intrathoracic pressure of the patient reaches athreshold amount. Also attached to the mask and the pressure-responsivevalve is a ventilatory source to provide ventilation to the patient. Theventilatory source may be any device or apparatus suitable for properlyventilating the patient. Preferably, the ventilation source will be anAMBU bag. When ventilation is needed, the AMBU bag may be squeezed toforce air into the patient's lungs. The AMBU bag is described in U.S.Pat. No. 5,163,424 which is incorporated herein by reference.

[0118] In an alternative embodiment, a ventilation source, preferably anAMBU bag, is used in connection with an improved endotracheal tube. Apressure-responsive valve or other flow restrictive element is placedbetween the AMBU bag and the endotracheal tube. Preferably, the valvewill be positioned within a tube that connects the AMBU bag to theendotracheal tube. The combination of the endotracheal tube with theAMBU bag with adapter can be included in the definition of a“ventilation tube.” Before ACD-CPR is performed on the patient, theendotracheal tube is placed in the patient's trachea. Duringdecompression of the patient's chest, the valve prevents airflow to thepatient's lungs until the intrathoracic pressure reaches a thresholdamount. Additionally, the AMBU bag may be used to ventilate the patientat a desired time. Also included in this embodiment is a one-wayexpiration valve. This valve allows for expiration of air from thepatient during the compression step.

[0119] In a modification of either of the first two embodiments, apressure-responsive expiration valve may also be inserted between theAMBU bag (or comparable ventilation source) and the mask or endotrachealtube. This valve works in a similar manner to the pressure-responsivevalve which restricts airflow into the patient's lungs. However, thepressure-responsive expiration valve restricts airflow from thepatient's lungs during the compression step of ACD-CPR. An equivalentvalve is a positive end-expiratory pressure (PEEP) valve available fromAMBU International, Copenhagen, Denmark. Use of such anpressure-responsive expiration valve during inhalation may furtherincrease intrathoracic pressure and thereby force more blood out of thethorax.

[0120] In another alternative embodiment, an improved endotracheal tubeis used to restrict airflow into the patient's lungs during the activedecompression step. Included in the endotracheal tube is a flowrestrictive element which operates to impede air from flowing into thepatient's lungs. When the endotracheal tube is inserted into thepatient's trachea and the patient's chest is actively decompressed, theflow restrictive element impedes air from flowing to the patient's lungsslowing the rise in intrathoracic pressure and thus enhancing bloodoxygenation.

[0121] When using the improved endotracheal tube during ACD-CPR,periodic ventilation of the patient will usually still be performed toenhance gas exchange to the patient. With the improved endotrachealtube, such manual ventilation may be accomplished by placing aventilation source at the opening of the endotracheal tube to forceoxygen through the endotracheal tube and into the patient's lungs.

[0122] Referring now to FIG. 2A, a schematic view illustrating airflowthrough a ventilation circuit 20 when compressing a patient's chestaccording to the present invention is shown. During ACD-CPR, the chestis actively compressed forcing air out of the lungs. This air is allowedto expire through a one-way expiration valve 22 within a ventilationcircuit 20.

[0123] Referring now to FIG. 2B, the same schematic is shownillustrating airflow through the ventilation circuit 20 whendecompressing the patient's chest. When the patient's chest is activelydecompressed, a negative intrathoracic pressure is created. When thispressure reaches a threshold amount, the inflow valve 24 will opencausing air to flow through the ventilation circuit 20 into thepatient's lungs. Air is allowed into the ventilation circuit 20 througha ventilation valve 26 and into a ventilation bag 28. From theventilation bag 28, the air passes through the inflow valve 24 when thenegative intrathoracic pressure reaches the threshold amount. Theventilation bag 28 is also used to manually ventilate the patient duringACD-CPR as required.

[0124] The method as discussed in connection with FIGS. 2A and 2Brequires the chest to be compressed in the range from about 3.5 cm to 5cm per compression and at a rate from about 60 to 100 compressions perminute for adults.

[0125] Referring now to FIG. 3, a schematic illustration of a firstalternative embodiment of a device 35 for impeding airflow into apatient's lungs according to the present invention is shown. The device35 comprises an endotracheal tube 36 which is placed into the patient'strachea and provides a ventilation passageway. Connected to theendotracheal tube 36 is a transition tube 38 which connects theendotracheal tube 36 to the ventilation bag 28. Although theendotracheal tube 36 is shown connected to the ventilation bag 28, theendotracheal tube 36 can be used alone or in connection with theventilation bag 28. The ventilation bag 28 can comprise any type ofventilation source capable of ventilating the patient such as acompressible or collapsible structure. Preferably, the ventilation bag28 consists of an AMBU bag. Attached or connected to the end of theventilation bag 28 is a one-way ventilation valve 26. The ventilationvalve 26 serves to introduce air into the device 35. Attached orconnected to the transition tube 38 is an inflow pressure-responsivevalve 24. The inflow valve 24 is biased so that it opens when thenegative intrathoracic pressure in the patient's chest reaches athreshold amount. As shown, only one inflow valve 24 is included in thedevice 35. However, the invention is not limited to only one inflowvalve 24. Alternatively, a plurality of inflow valves 24 could beconnected in series along the ventilation tube 38. The inflow valve 24is also not limited to being connected in the center of the transitiontube 38, but may be positioned anywhere along the transition tube 38.The inflow valve 24 could be permanently attached to the ventilation bag28 or transition tube 38 or could be detachable. Alternatively, theinflow valve 24 could be connected to the ventilation bag 28 itself orto the endotracheal tube 36.

[0126] The device 35 also contains a one-way expiration valve 22 whichallows for air to be expired from the patient's lungs. This generallyoccurs during the compression phase of ACD-CPR. To insure that the airexpired from the patient's lungs will exit through the expiration valve22, a one-way fish mouth valve 37 (the preferred valve) or any othertype of one-way valve can be placed between the inflow valve 24 and theexpiration valve 22. Alternatively, the inflow valve 24 itself may beconfigured as a one-way valve. In either case, air flowing from theendotracheal tube 36 toward the ventilation bag 28 will be forced toexpire through the expiration valve 22.

[0127] The device 35 may be further modified to include apressure-responsive expiration valve 39 (not shown) located between theendotracheal tube 36 and the transition tube 38. The pressure-responsiveexpiration valve works in a reverse manner to that of the inflow valve24. Specifically, the pressure-responsive expiration valve is biased sothat during the compression step of ACD-CPR, air will be allowed toexpire from the patient's lungs only when the intrathoracic pressurereaches a threshold amount. The increase in intrathoracic pressurecaused by the pressure-responsive expiration valve 39 during compressionmay assist in forcing more blood out of the thorax and reduceatelectasis of the lungs.

[0128] The purpose of the ventilation bag 28 is to provide ventilationto the patient during ACD-CPR. When the ventilation bag 28 comprises anAMBU bag or similar bag used for ventilation, ventilation of the patientmay be performed by merely squeezing the AMBU bag with a human hand.This forces air to the patient's lungs as desired.

[0129] Referring to FIG. 4A, a second alternative embodiment of thedevice for impeding airflow into a patient's lungs according to thepresent invention is shown. This particular embodiment is a modified andimproved endotracheal tube. Hence, the second alternative embodimentcomprises an endotracheal tube 36 having two lumens at its proximal end.The first lumen is an outflow lumen 40, and the second lumen is aninflow lumen 42. Located within outflow lumen 40 is a one-waypressure-responsive expiration valve 44 which operates in a mannersimilar to that discussed in connection with FIG. 3, except that theexpiration valve 44 is specifically designed as a one-way valve. Locatedwithin inflow lumen 42 is a one-way pressure-responsive inflow valve 45which operates to impede airflow to the lungs as discussed in connectionwith FIG. 3, except that the inflow valve 45 is also specificallydesigned as a one-way valve. Also shown in inflow lumen 42 and outflowlumen 40 is an O-ring 46 which will be discussed subsequently. Inflowvalve 45 and expiration valve 44 are designed as one-way valves so thatduring the compression phase, air can only be expired from the patientthrough the endotracheal tube 36 when the intrathoracic pressure reachesa threshold amount. At that moment, expiration valve 44 opens and airexpires from the patient through the outflow lumen 40. Duringdecompression, air cannot flow through the endotracheal tube 36 to thepatient's lungs until the negative intrathoracic pressure reaches athreshold amount. At that moment, inflow valve 45 opens allowing air toflow through inflow lumen 42 to the patient's lungs. Air is preventedfrom entering through the outflow lumen 40 because of the one-wayexpiration valve 44.

[0130] Ventilation is possible with the embodiment disclosed in FIGS. 4Aand 4B if the inflow lumen 42 is connected to a ventilation source suchas a ventilation bag. When the ventilation bag is squeezed, air isallowed to flow through the inflow lumen 42, through the endotrachealtube 36, and to the patient's lungs. In this embodiment, expirationvalve 44 is designed so that during ventilation, expiration valve 44will remain temporarily closed preventing air flowing through inflowlumen 42 escape through outflow lumen 40.

[0131]FIG. 5A is a schematic view of a one-way inflow valve 45 used in adevice for impeding airflow according to the present invention. Theinflow valve 45 operates so as to allow air only to flow in onedirection. As shown, the spring biased inflow valve 45 is completelyopen. However, the invention also functions properly if the springbiased inflow valve 45 or the spring biased expiration valve 44 are notfully open. Upon successful completion of ACD-CPR, the O-ring 46 that ispositioned above the inflow valve 45 is repositioned so that inflowvalve 45 is held open as shown in FIG. 5B. Such a positioning of O-ring46 allows for unimpeded airflow to the patient once there is a return ofspontaneous circulation and the inflow valve 45 is no longer needed. AnO-ring 46 is also used in a similar manner to lock the one-wayexpiration valve 44 in an open position upon return of spontaneouscirculation. FIG. 5C illustrates the one-way inflow valve 45 in a closedposition. When closed, the inflow of air through the inflow valve 45 isoccluded.

[0132]FIG. 6A illustrates an inflow valve 47 that is spring biased andan expiration valve 48 that is also spring biased. The inflow valve 47and the expiration valve 48 are connected in series and may be used inthe first alternative embodiment as discussed in connection with FIG. 3,or with the preferred embodiment discussed following in connection withFIG. 9. As shown in FIG. 6C, during the active decompression step, theinflow valve 47 is biased such that it will open when the negativeintrathoracic pressure reaches a threshold amount. During thecompression phase of ACD-CPR the expiration valve 48 will open to allowair to expire from the patient's lungs when the intrathoracic pressurewithin the patient's chest reaches a threshold amount as shown in FIG.6B. Since neither inflow valve 47 nor expiration valve 48 are one-wayvalves, a fish mouth valve 37 used in connection with a one-wayexpiration valve 22 as discussed in connection with FIG. 3 must be used.Other valves designed upon a similar principle as the fish mouth valvecombination with a one-way expiration valve could also be used. Only oneinflow valve 24 and one positive end pressure valve 44 are shown inFIGS. 6A-6C. However, a plurality of inflow valves 47 and/or expirationvalves 48 may be connected in a permanent or detachable manner in seriesto impede the inflow and outflow of air.

[0133] Although the valves in FIGS. 6A-6C are shown as beingspring-biased, any other valves designed upon a similar principle wouldwork equally as well. The use of such valves as disclosed in FIGS. 6A-6Cis only one embodiment and valves constructed according to various othermethods and materials is also within the scope of the invention.

[0134] As shown in FIG. 7, the inflow valve 47 and the expiration valve48 may be combined into one joint valve 49 as shown. The joint valve 49will operate in a manner similar to the two valves 47 and 48 asdescribed in connection with FIG. 6.

[0135]FIG. 8 illustrates a flow restricting orifice 50 to be used toeither impede the airflow into or out of a patient's lungs. The flowrestricting orifice 50 operates so that during the decompression step ofACD-CPR airflow is impeded from entering into the patient's lungs, thusincreasing the negative intrathoracic pressure. During the compressionstep, the flow restricting orifice 50 operates to increase the thoracicpressure in the patient's chest by restricting air from existing fromthe patient's lungs.

[0136]FIG. 9 illustrates an exemplary embodiment for impeding airflowinto a patient's lungs according to the present invention. As shown, thedevice 51 comprises a ventilation bag 28 that is connected to a facialmask 52 by an inflow valve 24 and an expiration valve 22. Although thefacial mask 52 is shown connected to the ventilation bag 28, the facialmask 52 can be used alone or in connection with the ventilation bag.Between the inflow valve 24 and the expiration valve 22 is a one-wayfish mouth valve 37 or any other type of one-way valve to prevent airfrom exiting the patient's lungs and flowing to the ventilation bag 28.The ventilation bag 28 also contains a one-way ventilation valve 26 forallowing air to inflow into the device 51. The exemplary embodimentoperates in a manner similar to that of the first alternative embodimentas discussed in connection with FIG. 3. However, instead of inserting anendotracheal tube 36 into the patient's airway, the facial mask 52 isplaced over the patient's mouth and nose. A facial strap 54 (not shown)may also be wrapped around the head of the patient to secure theventilation mask 52 to the patient's face.

[0137] Device 51 is preferably used in connection with an oral airwaydevice (not shown) to prevent the patient's airway from becomingoccluded, e.g. by the patient's tongue. The oral airway device can beany device that is used to keep the patient's tongue from slippingbackward and occluding the airway. Preferably, the oral airway devicewill be curved and constructed of a plastic material and may or may notbe attached to the device 51.

[0138] During the decompression phase of ACD-CPR, air is prevented fromentering into the patient's lungs through the threshold inflow valve 24thus increasing the negative intrathoracic pressure. During thecompression phase, air is allowed to expire from the patient's lungsthrough the expiration valve 22. Also, the patient can be ventilatedduring ACD-CPR by manually squeezing the ventilation bag 28.Consequently, the preferred embodiment serves to enhance cardiopulmonarycirculation by increasing the negative intrathoracic pressure to forcemore blood into the chest from the peripheral venous vasculature.

[0139] FIGS. 10A-10C show another embodiment of the present inventionwhich allows the patient to be ventilated by bypassing the impedingstep. The embodiment comprises a ventilation tube 60 with a proximal end62 and a distal end 64 that is connected to the patient. The ventilationtube 60 has a one-way bypass valve 66 and a one-way pressure responsivevalve 68. The ventilation tube 60 may also have a manual switch 70attached to the bypass valve 66 and extending through a side of theventilation tube 60. As shown in FIG. 10A, the switch 70 may be set in aclosed position so that the one-way pressure responsive valve 68 openswhen the threshold pressure of the valve 68 has been exceeded. At thispoint, the valve 68 opens allowing for ventilation of the patient. Asshown in FIG. 10B, the one-way pressure responsive valve 68 may bebypassed altogether by manually placing the switch 70 in the openposition so that the bypass valve 66 is opened allowing air to flow tothe patient. FIG. 10C illustrates the operation of the bypass valve 66with the switch 70 in an inactive mode. Here, the rescuer performingventilation may do so without added resistance from the impedance stepas in FIG. 10A. Instead, bypass valve 66 opens only when the pressure atthe proximal end of the tube 62 is greater than atmospheric pressure (0mmHg), preferably in a range from about 0 mmHg to 5 mmHg. Duringdecompression of the patient's chest, the one-way bypass valve 66remains closed unless atmospheric pressure is exceeded. Thus, thepatient is ventilated only when the rescuer performing ventilationcauses the pressure at the proximal end of the tube 62 to exceedatmospheric pressure. The function of the one-way bypass valve 66 may beperformed by many different threshold valve designs which are known inthe art.

[0140] In another aspect of the invention, an exemplary valving systemis provided for enhancing the duration and extent of negativeintrathoracic pressure during the decompression phase of CPR while stillproviding adequate ventilation to the patient. The valving system isemployed to slow the rapid equilibrium of intrathoracic pressure in thechest during decompression by impeding or inhibiting the flow of airinto the patient's chest. Lowering of the intrathoracic pressure in thismanner provides a greater coronary perfusion pressure and hence forcesmore venous blood into the thorax. The valving system can be employed ina variety of CPR methods where intrathoracic pressures are intentionallymanipulated to improve cardiopulmonary circulation, including “vest”CPR, CPR incorporating a Heimlich ventilatory system, intraposedabdominal compression-decompression CPR, standard manual CPR, and thelike, and will find its greatest use with ACD-CPR.

[0141] Referring to FIGS. 11-15, an exemplary embodiment of a valvingsystem 100 is shown schematically. The valving system 100 includes ahousing 101 having an upstream region 102 and a downstream region 104.Held between the upstream region 102 and downstream region 104 is adiaphragm 106. The diaphragm 106 is preferably a flexible or elastomericmembrane that is held over the downstream region 104 to inhibit air fromflowing from the upstream region 102 to the downstream region 104 whenthe pressure in the downstream region 104 is less than the pressure inthe upstream region 102, except when positive pressure, i.e. greaterthan atmospheric, is developed in the upstream region 102 whenventilating the patient. The valving system 100 further includes a valve108 having a plug 110. As described in greater detail hereinafter, thevalve 108 is included to provide ventilation to the patient when opened.The valve 108 can be manually opened by axial translation or it can beautomatically opened when the pressure in the downstream region 104reaches or exceeds a threshold amount, or both. Included at the upstreamregion 102 is an air intake opening 112 and an air exhaust opening 114.Air is delivered into the housing 101 through the air intake opening112, while air is exhausted from the housing 101 through the air exhaustopening 114. An accordion valve 116, fish mouth valve, or the like isprovided between the air intake opening 112 and the air exhaust opening114. As described in greater detail hereinafter, the accordion valve 116is used to prevent air that is injected into the air intake opening 112from exiting the air exhaust opening 114 when ventilating the patient. Afilter 117 is provided for filtering air injected into the housing 101.Optionally, a filter 119 can be provided in the downstream region 104for preventing excess body fluids and airborne pathogens from enteringinto the system 100.

[0142] Operation of the valving system 100 during compression of apatient's chest is illustrated in FIG. 11. As the patient's chest iscompressed, air is forced from the patient's lungs and into thedownstream region 104. The air forced into the downstream region 104 isdirected against the diaphragm 106 forcing the diaphragm into an ambientpressure region 118. Air in the downstream region 104 is then allowed toescape into the upstream region 102 where it is exhausted through theair exhaust opening 114. Optionally, the diaphragm 106 can be biased sothat it will not be forced into the ambient pressure region 118 untilthe pressure within the downstream region 104 is about 2 cm H₂O orgreater, and more preferably at about 2 cm H₂O to 4 cm H₂O.

[0143] Operation of the valving system 100 during decompression (orresting) of the patient's chest is illustrated in FIG. 12. As thepatient's chest is actively lifted (or allowed to expand on its own),air is drawn from the downstream region 104 and into the patient'slungs, thereby reducing the pressure in the downstream region 104. Theresulting pressure differential between the regions 102, 104 holds thediaphragm 106 over the downstream region 104 to prevent air from theupstream region 102 from flowing to the downstream region 104. In thisway, air is inhibited from flowing into the patient's lungs duringdecompression of the patient's chest, thereby lowering the intrathoracicpressure to increase the coronary perfusion pressure and to force morevenous blood into the thorax.

[0144] Various ways of providing ventilation to the patient using thevalving system 100 are described in FIGS. 13-15. FIG. 13 illustratesairflow into the downstream region 104 and to the patient's lungs duringdecompression of the patient's chest after a threshold amount ofnegative intrathoracic pressure has been reached. Ventilation in thismanner is advantageous in that the valving system 100 can be employed toproduce at least a threshold amount of intrathoracic pressure to enhanceblood flow into the heart and lungs. Once such as pressure is reached,some air is allowed to flow to the patient's lungs to ventilate thepatient.

[0145] Air is allowed to enter the downstream region 104 when thethreshold amount of intrathoracic pressure is reached by configuring thevalve 108 to be a threshold valve. The valve 108 can be configured in avariety of ways, with a primary function being that the valve 108 allowsair to flow into the downstream region 104 when a threshold amount ofintrathoracic pressure is reached. This is preferably accomplished byconfiguring the plug 110 to be flexible in one direction so that whenthe pressure in the downstream region 104 reaches or exceeds thethreshold amount, the plug 110 is flexed to provide an opening 126between the upstream region 102 and downstream region 104. When the plug110 is flexed, air flows from the lower pressure upstream region 102into the downstream region 104 and to the patient's lungs. The plug 110therefore acts as a one-way valve allowing air to flow from the upstreamregion 102 into the downstream region 104 when the threshold amount isreached, but does not allow airflow from the downstream region 104 tothe upstream region 102. Preferably, the plug 110 will flex to open whenthe pressure within the downstream region 104 is in the range from about0 mm H₂O to 50 cm H₂O, more preferably at about 10 cm H₂O to 40 cm H₂O,and more preferably at 15 cm H₂O to about 20 cm H₂O. Alternatively, thevalve 108 can be placed in the downstream region 104 so that air flowsinto the downstream region 104 directly from the atmosphere when thevalve 108 is open. Although shown as a flexible plug, it will beappreciated that other types of valve arrangements may be used. Forexample, plug 110 could be replaced with a spring biased valve thatcloses opening 126 until the negative intrathoracic pressure overcomesthe force of the spring to open the valve in a manner similar to thatdescribed in connection with FIG. 16A.

[0146] Ventilating the patient by injecting air into the upstream region102 is illustrated in FIG. 14. As air is injected through the intakeopening 112, it passes into the accordion valve 116 and forces the valve116 against a wall 120 and covers a hole 122 in the wall 120 to preventairflow through the exhaust opening 114. When the accordion valve 116 isclosed, air flows through a wall 124 of the valve 116 and into theupstream region 102. Alternatively, a fish mouth valve can be used inplace of the accordion valve 116. Upon injection of the air into theupstream region 102, the pressure within the upstream region 102 becomesgreater than the pressure in the ambient pressure region 118 and causesthe diaphragm 106 to be drawn into the ambient pressure region 118. Anopening between the upstream region 102 and the downstream region 104 iscreated allowing air to flow into the downstream region 104 and into thepatient's lungs. Preferably, the patient will be manually ventilated byinjecting air into the intake opening 112 one time every fivecompressions of the chest, and more preferably about two times every 15compressions of the chest using two rescuers. Similarly, ventilating thepatient can occur through the same port where the spring-biased valve islocated, such as through valve 160 of FIG. 16A.

[0147] Configuration of the valving system 100 upon return ofspontaneous circulation is illustrated in FIG. 15. When the patient'scirculation is restored, the valve 108 is manually opened by translatingthe valve 108 to remove the plug 110 from aperture 126. The upstreamregion 102 and downstream region 104 are then placed in communication toallow air to be freely exchanged between each of the regions 102, 104.Although shown extending through the upstream region 102, the valve 108can alternatively be placed anywhere along the downstream region 104.

[0148] The valve 108 can be configured as a pressure-responsive valve(see FIG. 13), as a manually operable valve (see FIG. 15), or both.Further, the valving system 100 can alternatively be provided with twoor more valves that are similar to the valve 108. For example, one valvecould be non-translatably held in the housing 101 and provided with apressure-responsive plug 110, with the other valve being translatablymounted. In this manner, the valve with the flexible plug functions as apressure-responsive valve and opens when the threshold pressure isreached, while the translatable valve functions to place the regions102, 104 in communication upon manual operation after spontaneouscirculation is achieved.

[0149] Referring to FIGS. 16A and 16B, an exemplary embodiment of avalving system 130 will be described. The valving system 130 isconstructed of a housing 132 having an intake opening 134, an exhaustopening 136, and a delivery opening 138. Included in the exhaust opening136 is a one-way valve 140 which allows air to flow from the housing 132and out the exhaust opening 136. An accordion valve 140 is providedbetween the intake opening 134 and an exhaust opening 136 to prevent airinjected into the intake opening 134 from exiting through the exhaustopening 136. Preferably, the intake opening 134 is configured to beattachable to a respiratory device, such as a respiratory bag (includingan AMBU bag), a ventilator, a mouthpiece or port for mouth-to-mouthbreathing through the system 130, or the like. The delivery opening 138is preferably configured for connection to an endotracheal tube or otherairway tube, a sealed facial mask, a laryngeal mask, or the like.

[0150] Within the housing 132 is an upstream region 142, a downstreamregion 144, and an ambient pressure region 146. Separating the upstreamregion 142 from the downstream region 144 is a diaphragm 148. Thediaphragm 148 is preferably constructed of an elastomeric material. Thehousing 132 is preferably cylindrical in geometry at the downstreamregion 144, with the diaphragm 148 resting on the cylinder duringambient conditions. During decompression of the patient's chest, thereduction in pressure in the downstream region 144 draws the diaphragm148 against the end of the cylinder to prevent exchange of air betweenthe upstream region 142 and downstream region 144. During compression ofthe patient's chest, air is forced into the downstream region 144 toforce the diaphragm 148 into the ambient pressure region 146 so that theair exhausted from the patient's chest can be exhausted through theexhaust opening 136.

[0151] As shown best in FIG. 16B, the valving system 130 is furtherprovided with a fenestrated mount 150. In one aspect, the fenestratedmount 150 serves as a mount for holding the diaphragm 148 over thedownstream region 144. The fenestrated mount 150 further provides theambient pressure region 146. Fenestrations 152 are provided in the mount150 to allow air to be exchanged through the mount 150. Included on themount 150 is a deflector 154 for deflecting air around the fenestratedmount 150. Various other deflectors 156 are provided in the housing 132for directing airflows between the regions 142 and 144. A filter 158 isprovided in the housing 132 to filter air injected into the housing 132.Optionally, a filter 159 can be provided to prevent excess body fluidsfrom entering into the system 130.

[0152] The valving system 130 further includes a threshold valve 160 atthe downstream region 144. When the pressure within the downstreamregion 144 is less than the threshold amount, the threshold valve 160 isopened to allow air to flow into the downstream region 144. Thethreshold valve 160 includes a spring 162 which is configured to extendwhen the threshold amount is reached. Alternatively, the threshold valve160 can be configured similar to the valve 110. Other configurationswhich allow the for air to enter the downstream region 144 when thedesired intrathoracic pressure is reached or exceeded can also beprovided. For example, in a further alternative, the diaphragm 148 canbe constructed to function as a threshold valve to allow air to flowinto the patient's lungs when a threshold amount of intrathoracicpressure is reached. The diaphragm 148 can be fashioned as a thresholdvalve by constructing the diaphragm 148 of an elastomeric material andby providing at least one hole near the periphery. When the diaphragmrests on the cylinder forming the downstream region 144, the hole ispositioned beyond the periphery of the cylinder and in the upstreamregion 142. As a vacuum is created in the downstream region 144, thediaphragm is drawn into the downstream region 144 until the hole isstretched over the cylinder and overlaps with both the upstream region142 and the downstream region 144. In this way, a fluid path is providedbetween the regions 142 and 144 when the threshold pressure is reachedin the downstream region 144. Another alternative of a threshold valve111 is illustrated in FIG. 16C. The valve 111 is pivot mounted withinthe downstream region 144 and is biased closed by a spring 113. When thethreshold pressure within the downstream region 144 is reached, thespring 113 is compressed and air is drawn into the downstream region144.

[0153] Referring back to FIG. 16A, the threshold valve 160 canoptionally be provided within the housing 132 at the upstream region142. The threshold valve 160 can further optionally be provided with anon/off switch for opening the valve 160 when spontaneous circulation isachieved. In this manner, a rescuer can open the valve 160 to allow forfree exchange of air to the patient's lungs when needed. In onealternative as shown in FIG. 16C, the mount 150 can be slidably mountedwithin the housing 132 so that the mount 150 can be vertically raised tolift the diaphragm 148 from the downstream region 144 upon successfulresuscitation of the patient, thereby providing a free flow of air tothe patient. The mount 150 can be slidably mounted within the housing132 by attaching the mount 150 to an extension member 133 that isslidable within the housing 132. The member 133 preferably includes theintake and exhaust openings 134 and 136. In this way, an easy graspingsurface is provided when translating the member 133 to open or close thediaphragm 148. If the diaphragm 148 were also fashioned as a thresholdvalve as previously described, the need for the valves 108 or 111 couldbe eliminated.

[0154] The housing 132 can conveniently be constructed in several partswhich are connected together at various connection points. In thismanner, the housing can be taken apart for connection to other devices,for repair, for cleaning, and the like. For example, one connectionpoint can be conveniently provided near the filter 158 for removablyconnecting the portion of the housing having the intake opening 134, thevalve 140, and the exhaust opening 136. Alternatively, a connectionpoint can be provided near the mount 150 to provide easy access to themount 150 for cleaning.

[0155] The valving system 130 can conveniently be incorporated with avariety of devices useful in CPR procedures. For example, the valvingsystem 130 can be incorporated within a respiratory bag, such as an AMBUbag. Alternatively, the valving system 130 can be included as part of arespiratory circuit having both a respiratory bag and an endotrachealtube or other airway tube, with the valving system 130 positionedbetween the bag and the tube. In further alternative, the valving system130 can be added to an endotracheal tube alone. Alternatively, thevalving system can be incorporated into a mask, an oralpharyngealairway, a laryngeal mask or other ventilatory devices.

[0156] In some cases, patient ventilation may be provided throughthreshold valve 160 as shown in FIG. 16D. In such a case, intake openingand valve 140 are optional since all ventilation may occur throughthreshold valve 160. Of course, ventilation could be provided throughboth avenues. Further, although shown in the context of valving system130, it will be appreciated that the other embodiments described hereinmay be modified to include a pressure source that is coupled to thethreshold valve.

[0157] As shown in FIG. 16D, a tank 300 of pressurized gas, such as 02is coupled to housing 132 by a length of tubing 302. In this way, apressurized gas may be supplied to the back side of threshold valve 160.A regulator 304 is coupled to tank 300 to regulate the pressure suppliedto threshold valve 160 so that it is less than the pressure required toopen valve 160. For example, if respiratory gases are to be supplied tothe patient when the negative intrathoracic pressure exceeds −14 cm H₂O,then the actuating valve pressure may be set at −14 cm H₂O, and thepressure of the gas from tank 300 may be set less than 14 cm H₂O. Inthis way, valve 160 will not prematurely open. In some cases, regulator304 may also be used to regulate the flow rate of the gas through valve160.

[0158] By coupling tank 300 to valve 160, respiratory gases are pulledinto downstream region 144 when valve 160 opens due to the decrease innegative intrathoracic pressure as previously described. In this way,more respiratory gases are supplied to the patient each time thepatient's chest is decompressed. This approach allows for negativepressure ventilation, unlike positive pressure ventilation which impedesvenous return to the chest with each active rescuer ventilation. Thenegative pressure ventilation with this approach allows for adequateoxygenation and maximum venous blood return during CPR. Tank 300 mayalso function to provide oxygen once the trigger pressure has beenachieved.

[0159] Referring to FIG. 17, an alternative valving system 164 will bedescribed. The valving system 164 is shown schematically and operatesessentially identical to the valving system 100, the difference beingthat the valving system 164 includes a ball or spherical member 166 asthe diaphragm. During decompression of the patient's chest, the pressurein a downstream region 168 is less than the pressure in an upstreamregion 170 which draws the ball 166 over the downstream region 168. Thevalving system 164 can optionally be provided with a spring 172 or otherbiasing mechanism to hold the ball 166 over the downstream region 168during compression of the patient's chest until a threshold pressure isreached or exceeded in the downstream region 168 as previouslydescribed.

[0160] Referring now to FIG. 18, another exemplary device 200 which isuseful when performing cardiopulmonary resuscitation will be described.As described in greater detail hereinafter, one important feature ofdevice 200 is that it may be interfaced to the patient's airway toperiodically supply air to the patient's lungs when performingcardiopulmonary resuscitation. In this way, the patient may beventilated with air (or other desired gases, such as O₂) rather thanwith respiratory gases from the rescuer's lungs as is typically the casewhen performing mouth-to-mouth resuscitation.

[0161] Device 200 comprises a facial mask 202 and a housing 204 that isoperably attached to facial mask 202 at an interface 206. Housing 204includes an upper region 208 and a lower region 210. Lower region 210includes a pressure responsive valving system 212 which operates in amanner similar to the embodiments previously described herein to preventthe flow of gases into the patient's lungs until a threshold negativeintrathoracic pressure is exceeded. At this point, pressure responsivevalving system 212 allows gases to flow into the patient's lungs in amanner similar to that previously described herein. Lower region 210further includes a fish mouth valve 214 and one-way outflow valves 216.Valves 214 and 216 operate together to allow gases exhausted from thepatient's lungs to exit device 200 as indicated by arrow 218. Inparticular, when gases are forced out of the patient's lungs, fish mouthvalve 214 will be closed and the exhausted gases will escape from device200 through valves 216.

[0162] Upper region 208 includes a mouth piece 219 to allow a rescuer toblow into device 200 when attempting to ventilate a patient (similar toconventional CPR). Upper region 208 defines an air chamber 220 forholding room air and has a volume of about 200 ml to about 800 ml.Chamber 200 may also be connected to an oxygen source. Disposed withinupper region 208 is a diaphragm 222 and a spring 224. With thisconfiguration, when a rescuer blows air into mouth piece 219, spring 224will compress as diaphragm 222 moves downward. In turn, air or oxygenheld within air chamber 220 will be compressed and hence forced throughvalving system 212 and into facial mask 202. In this way, air (ratherthan respiratory gases) from the rescuer will be supplied to the patientwhen the rescuer performs mouth-to-mouth resuscitation by blowing intomouth piece 219.

[0163] Upper region 208 further includes a one-way inflow valve 226which allows air chamber 220 to be replenished with room air followingventilation. In particular, as spring 224 expands valve 226 will open toallow room air to fill chamber 230 due to the negative pressure createdin chamber 230 by spring 224. Inflow valve 226 will also open when thethreshold negative intrathoracic pressure is exceeded causing pressureresponsive valving system 212 to open. In this way, inflow valve 226also serves as a venting mechanism to vent air into housing 204 when thenegative intrathoracic pressure limit is exceeded.

[0164] Hence, device 200 allows a rescuer to ventilate a patient withroom air simply by blowing into mouth piece 219. Of course, it willappreciated that other desirable gases may be placed within air chamber220 so that such gases may be supplied to the patient when the rescuerblows into mouth piece 219. For example, a volume of O₂ may be placedwithin chamber 220.

[0165] As previously described, one aspect of the invention is theability to prevent respiratory gasses from entering the lungs until acertain negative intrathoracic pressure is met or exceeded. One aspectof the invention is the ability to vary the pressure at whichrespiratory gasses are permitted to flow to the lungs. In some cases,this may be accomplished by varying the actuating or cracking pressureof the pressure-responsive inflow valve. However, other mechanisms maybe provided to vary the pressure at which respiratory gasses arepermitted to flow to the lungs without modifying the cracking pressureof the pressure-responsive inflow valve. Hence, mechanisms for varyingthe pressure at which respiratory gasses are permitted to flow to thelungs may be incorporated in the pressure-responsive inflow valve,another valve in the valving system, or may be a separate part of theoverall valving system.

[0166] Such a system may be configured so that the actuating pressuremay vary between about 0 cm H₂O to about −30 cm H₂O. Further, such avalving system may be used alone with a spontaneous breathing patient orwith a patient receiving standard manual closed-chest CPR. Such avalving system may also be used in conjunction with other resuscitationtechniques and/or devices, including, for example, ACD CPR, Vest CPR, orthe like. In some cases, such a valving system may be used in connectionwith a diaphragmatic stimulator for purposes of resuscitation fromcardiac arrest as well as for increasing blood pressure by advancingvenous return. Exemplary systems and techniques for diaphragmaticstimulation for purposes of resuscitation are described in U.S. patentapplication Ser. No. 09/095,916, filed Jun. 11, 1998; Ser. No.09/197,286, filed Nov. 20, 1998; Ser. No. 09/315,396, filed May 20,1999; and Ser. No. 09/533,880, filed Mar. 22, 2000, incorporated hereinby reference. As a further example, such a valving system may be used toimprove central blood return to the heart in patients in cardiac arrest,patients with low blood pressure and patients in right heart failure andin shock.

[0167] A variety of mechanisms may be used to vary the degree at whichrespiratory gasses are permitted to flow to the lungs. For example, sucha mechanism may be mechanical or electronic or may include variouscombinations of mechanical and electronic components, and may beregulated within a larger system by, for example, electroniccommunication between the device used for resuscitation and thepressure-responsive inflow valve. Such a mechanism may also beadjustable based upon the in-line measurement of gasses, such as themeasurement of end-tidal CO₂, the average minute ventilations, peaknegative inspiratory pressures, and the like.

[0168] Referring to FIG. 19, one embodiment of a valving system 400having an adjustable pressure-responsive inflow valve 402 will bedescribed. Valving system 400 is shown schematically and may beconstructed similar to any of the embodiments described herein. As such,when valving system 400 is interfaced with a patient's airway, thepatient may freely exhale through valving system 400. When attempting toinhale, or during a decompression step of CPR, respiratory gasses areprevented from entering the lungs until a threshold actuating pressureis reached. At such time, respiratory gasses are permitted to flow tothe lungs through inflow valve 402 in a manner similar to thatpreviously described with other embodiments.

[0169] Inflow valve 402 includes a tension adjust knob 404 that may beturned by the rescuer to adjust the threshold actuating pressure ofinflow valve 402 and will be described in greater detail with referenceto FIGS. 20-22. As best shown in FIG. 20, inflow valve 402 comprises anouter housing 406 having a set of tracking channels 408 (see FIG. 22).Outer housing 406 is configured to hold an O-ring housing 410 having atop segment 412 and a bottom segment 414. Disposed between top segment412 and bottom segment 414 is an O-ring 416. Top segment 412 furtherincludes a set of tracking rails 418 that slide within tracking channels408. A tension spring 420 sits between tension adjust knob 404 and topsegment 412 and biases O-ring 416 against outer housing 406. When O-ring416 is biased against outer housing 406 the valve is in the closedposition where respiratory gasses are prevented from passing throughventilation ports 422 and to the patient's lungs. When the negativeintrathoracic pressure meets or exceeds the threshold actuating pressureof inflow valve 402, the tension in spring 420 is overcome, causingO-ring 416 to separate from outer housing 406. At this point,respiratory gasses are free to rush through ventilation ports 422 and tothe patient's lungs.

[0170] To vary the actuating pressure of inflow valve 402, knob 404 isturned to advance or retract a threaded nut 424 along a threaded bolt426 that in turn is coupled to top segment 412. In so doing, the tensionof spring 420 is varied to vary the actuating pressure of inflow valve402. Hence, knob 404 provides a convenient way for a rescuer to adjustthe actuating pressure simply by turning knob 404. Although not shown, apressure gauge may be disposed within valving system 400 and a displaymay be provided to display the negative intrathoracic pressure. In thisway, the rescuer may readily visualize the pressures generated withinvalving system 400 and may adjust knob 404 to vary the pressure at whichrespiratory gasses are permitted to flow to the lungs.

[0171] Another feature of the invention is the use of a safety mechanismto permit respiratory gasses to freely flow to the patient through thevalving system until the rescuer places the valving system in anoperative mode. Once in the operative mode, the valving system willremain in that mode indefinitely or for a finite period of time, atwhich the safety mechanism would revert back to its initial state whererespiratory gasses may freely flow to the lungs. In some embodiments,this may be accomplished by having the safety mechanism maintain thepressure responsive inflow valve in the open position (without anyimpedance to inspiratory air flow) until actuated by the rescuer.Actuation may be accomplished in a variety of ways, such as by injectedrespiratory gasses into the valving system (such as when ventilating thepatient), by operating a button or switch on the valving system, or thelike.

[0172] One advantage of such a safety mechanism is that it ensures thatthe patient can freely breathe through the valving system (assuming thepatient is spontaneously breathing or begins to spontaneous breathe)without any resistance from the pressure-responsive inflow valve. Oncethe rescuer is ready to begin a procedure, such as performing CPR, thevalving system is placed in the operative mode where respiratory gasflow to the lungs is prevented through the pressure-responsive inflowvalve until the threshold negative intrathoracic pressure is met orexceeded. As with other embodiments described herein, respiratory gassesmay also be injected into the patient's lungs through the valvingsystem, thereby bypassing the pressure-responsive inflow valve.

[0173] The safety mechanism may operate as a purely mechanical device, apurely electronic device, or may include various combinations ofmechanical and electronic components. One way for placing the valvingsystem in the operative mode is by utilizing a sensor to detect whenrespiratory gasses are injected into the valving system through theventilator port. The signal from the sensor may then be used to close aventilation passage within the valving system. In some cases, theventilation passage may extend through the pressure-responsive inflowvalve. To close this passage, the inflow valve is simply closed. In someembodiments, if rescuer ventilation is not provided within a certaintime, the safety mechanism may be used to take the valving system out ofits operative mode so that respiratory gasses may freely flow to thepatient's lungs.

[0174] Referring now to FIGS. 23 and 24, one embodiment of a valvingsystem 430 with such a safety feature will be described. Thisconfiguration may be used in series with any of the previously describedvalving systems so that it will have a means of impeding airflow to thepatient's lungs. Hence, it will be appreciated that valving system 430may be constructed to have, or used in combination with, componentssimilar to the other valving systems described herein and will not beillustrated to simplify discussion. Valving system 430 includes ahousing 432 that may be similar to the housings of the other valvingsystems described herein except that housing 432 includes a safetyventilation port 434 that permits respiratory gasses to flow into andthrough housing 432 so that respiratory gasses may flow to the patient'slungs as shown by the dashed line in FIG. 23. Hence, as shown in FIG.23, valving system 430 is in a passive mode where the patient may freelybreathe through housing 432.

[0175] Valving system 430 further includes a safety mechanism 436 thatis operative to maintain ventilation port 434 open until actuated by arescuer. When actuated, safety mechanism 436 closes ventilation port 434to place valving system 430 in the operative mode where respiratorygasses are prevented from reaching the lungs through apressure-responsive inflow valve until a threshold negativeintrathoracic pressure is met or exceeded in a manner similar to thatdescribed in other embodiments.

[0176] Safety mechanism 436 comprises an electronic air flow sensor 438that is electrically connected to control circuitry 440. In turn,control circuitry 440 is electrically connected to a micro-solenoid 442having a valve stop 444. A battery 445 is used to supply power to theelectrical components. When a rescuer is ready to place valving system430 in the operative mode, the rescuer injects respiratory gasses intohousing 432 (such as by blowing air or injecting a pressurized gas intoa ventilation port, not shown). As the respiratory gasses flow to thepatient's lungs through housing 432, sensor 438 is moved to trigger aswitch and to send an electrical signal to control circuitry 440.Control circuitry 440 then sends a signal to solenoid 442 to move stop444 and thereby close the valve, thus preventing airflow to the patientthrough safety ventilation port 434. Such a state is illustrated in FIG.24 where valving system 430 is in the operative mode. At this point, aspontaneously breathing patient will need to breathe through apressure-responsive inflow valve. For a non-breathing patient,respiratory gasses will be prevented from reaching the lungs during theperformance of CPR until a threshold negative intrathoracic pressure isovercome, at which point respiratory gasses may flow through the inflowvalve and to the patient's lungs in a manner similar to that describedwith other embodiments. If, after a certain time, sensor 438 is notactuated by the rescuer, control circuitry 440 may be configured tooperate solenoid 442 to take valving system 430 out of the operativemode where respiratory gasses may flow through safety ventilation port434.

[0177] In some embodiments, the valving systems of the invention mayincorporation a safety mechanism having essentially all mechanicalelements. One such embodiment of a valving system 480 is illustrated inFIGS. 25 through 33 and 36 through 40. Valving system 480 comprises ahousing 482 that houses various components that may be similar to theother embodiments described herein. As such, housing 482 includes aventilation port 484 and an exit opening 486. Valving system 480 furtherincludes a pressure-responsive inflow valve 488 that preventsrespiratory gasses from flowing to the patient's lungs until a certainnegative intrathoracic pressure level has been met or exceeded in amanner similar to that described with other embodiments. Valving system480 further includes a safety mechanism 490 to permit respiratory gassesto freely flow to the patient's lungs until operated to place valvingsystem 480 in an operative mode where pressure-responsive inflow valve488 controls when respiratory gasses are permitted to flow to the lungs.As described in greater detail hereinafter, safety mechanism 490 alsoincludes an inflow valve 492. In some embodiments, inflow valve 492 maybe configured as a pressure-responsive inflow valve and therebyeliminate the need for inflow valve 488.

[0178] Safety mechanism 490 further comprises a flow sensor 494 that isin the form of a flap. Flow sensor 494 pivots about a pivot point 496 tomove a cam mechanism 498, thereby rotating a wheel 500. In FIGS. 25 and30, valving system 480 is in the inactive state where flow sensor 494has not yet been activated. When respiratory gasses are directed throughhousing 482, flow sensor 494 pivots about pivot point 496 as previouslydescribed to rotate wheel 500 as illustrated in FIGS. 27, 28 and 30.

[0179] As best shown in FIG. 29, wheel 500 is connected to a gear system502 having a recoil spring 504 and a valve cam 506. Recoil spring 504 isemployed to bias cam 506 in the position illustrated in FIGS. 25 and 30where valve 492 is in the open position. When gasses flow throughhousing 482, flow sensor 494 is moved to cause wheel 500 to rotate andthereby operate gear system 502. In so doing, cam 506 is rotated to theposition shown in FIGS. 27 and 31 where valve 492 moves to the closedposition. Gear system 502 and recoil spring 504 operate to open valve492 after a certain period of time has elapsed, such as about 10 to 20seconds.

[0180] As best shown in FIGS. 30 and 31, valve 492 comprises a valvehousing 508 in which is held a valve shaft 510 that holds an O-ring 512.A tension spring 514 is positioned between housing 508 and a projection516 on shaft 510 to bias the valve 492 in the closed position asillustrated in FIG. 31. When a rescuer injects respiratory gasses intothe housing of the valving system, cam 506 moves to the position shownin FIG. 30 where it engages shaft 510 and disengages O-ring 512 fromhousing 508 to place valve 492 in the open position. In the openposition, respiratory gasses are free to flow through valve 492 and intohousing 482 where they may flow to the patient's lungs through exitopening 486.

[0181] The invention further provides systems having safety featuresthat allow for the patient to inhale to a given degree to release themechanism that is used to impede or prevent respiratory gases fromflowing to the lungs, thereby allowing for resistance free inspirationuntil a timer resets the systems or until the rescuer resets the system.One embodiment of a safety valve 600 that may be used with such systemsis illustrated in FIGS. 32 and 33. Safety valve 600 may be used as areplacement for any of the pressure responsive valves described herein,such as, for example, valves 108, 160 and 111. Valve 600 comprises ahousing 602 which is covered by a slit membrane 604. A valve member 606is biased by a spring 608 into a closed position as shown in FIG. 32. Inthe closed position, a wedge 610, that may conveniently be colored foreasy identification, extends above the slit in membrane 604. As such,wedge 610 serves as a visual indicator to the rescuer that valve 600 isin the closed position. When interfaced with a patient and in the closedposition, respiratory gases may be prevented from flowing to the lungsuntil the negative intrathoracic pressure meets or exceeds a thresholdvalue in a manner similar to that described with other embodiments. Atsuch time, a seal 612 on valve member 606 moves away from a stop 614 onhousing 602 to permit respiratory gases to flow to the lungs. Spring 608then forces valve member 606 back to the closed position.

[0182] If the patient gasps and begins to breath, the amount of negativepressure created by the patient compresses spring 608 far enough so thatwedge 610 is pulled through the slit in membrane 604 as shown in FIG.33. Wedge 610 then holds valve 600 in the open position where gases mayfreely flow to the lungs. The rescuer may easily determine valve 600 isin the open position by noticing that wedge 610 is no longer visible.The rescuer may reset valve 600 at any time by simply pulling on a pulltab 616 to pull wedge 610 back through membrane 604.

[0183] Another embodiment of a safety valve 620 that may be used in thesystems described herein is illustrated in FIGS. 34 and 35. Valve 620comprises a housing 622 having a stop 624. A micro-solenoid 626 isdisposed within housing an includes an arm 628 having a pole magnet 629and a visual indicator 630 at an opposite end. Spaced apart from polemagnet 629 is another pole magnet 632 of opposite polarity that iscoupled to a valve member 634 having a seal 636. Coupled to housing 622is a normally open contact strip switch 638, and valve member 634includes a conductive strip 640. A spring 642 is disposed between strip640 and stop 624.

[0184]FIG. 34 illustrates valve 620 in the closed or active position.During CPR, seal 636 will separate from stop 624 to permit respiratorygases to flow to the lungs when the negative intrathoracic pressureexceeds a threshold value. Valve 620 then returns back to the closedposition. If the patient gasps, valve member 634 moves to the positionshown in FIG. 35 where conductive strip 640 contacts switch 638. (Duringnormal CPR, valve member 634 is not moved far enough for this contact tooccur). This closes the open circuit and activates solenoid 626 toextend arm 628 and trigger a timing circuit within a control circuitryand battery compartment 644. Magnets 629 and 632 have opposite polescausing valve to remain in the open and inactive position as shown inFIG. 35 as long as solenoid 626 is actuated. In this way, the patientmay continue to freely breath through valve 620. Although shown withopposing pole magnets, it will be appreciated that magnets may besubstituted with a solenoid arm that may act as a plunger to makephysical contact with valve member 634, and thus hold the valve open andinactive. The rescuer may note that valve 620 is in the open position bynoting that indicator 630 has been retracted and is no longer visible.

[0185] Valve 620 may include an auto/manual switch 646 that may be setin automatic mode. In this mode, the timing circuit automaticallydeactivates solenoid 626 and returns valve 620 back to the closed andactive position shown in FIG. 34 after a preset timing interval hasexpired. If switch 646 is set to manual, solenoid 626 remains active andvalve 620 remains open and inactive as shown in FIG. 35 whererespiratory gases may freely flow to the lungs. Valve 620 remains openuntil the rescuer manually resets solenoid 626 by pressuring a manualreset switch 648. The rescuer may note that valve 620 is closed andactive by observing indicator 630 that is now extended.

[0186]FIGS. 36 and 37 illustrate a further embodiment of a safety valve650 that may be used with the systems described herein. Valve 650comprises a housing 652 having a stop 654. Disposed within housing 652is a valve member 656 having a seal 658 that contacts stop 654 toprevent gases from flowing through valve 650 when in the closed oractive position shown in FIG. 36. In the closed position, a spring 660biases seal 658 against stop 654 until the negative intrathoracicpressure exceeds a threshold value and seal 658 moves away from stop 654to permit respiratory gases to flow to the lungs. Once the negativeintrathoracic pressure falls below the threshold value, valve 650 movesback to the closed position.

[0187] When the patient gasps, the force created is great enough to movevalve member 656 such that a pair of spring loaded pins 662 lodge withingrooves 664 of a locking pin receptacle 666 on valve member 656 as shownin FIG. 37. In this way, valve 650 is locked into an open or inactiveposition that is created by the patient's gasp. As pins 662 move intogrooves 664, the ends of pins 662 move into housing 652 to indicate tothe rescuer that the valve is inactive. Conveniently, the ends of pins662 may be colored to make them more visible to the rescuer. Toreactivate valve 650, the rescuer may pull upward on a pull tab 668 onvalve member 656. This releases pins 662 from grooves 664 and permit thevalve to spring back to the closed position of FIG. 36.

[0188] Referring now to FIGS. 38-40, a modified version valve 650 isshown incorporated into a valve system 670 that may be coupled to apatient's airway in a manner similar to the other valve systemembodiments described herein to regulate the airflow to the patient'slungs during a CPR procedure. For convenience of discussion, identicalelements of valve 650 will use the same reference numerals in describingFIGS. 38-40. The use of valve 650 allows the patient to gasp and breathefree of airway resistance after the initial gasp has occurred.Alternatively, valve 650 may be initially set in the inactive positionand placed in the active state upon the initial ventilation throughvalve system 670, or upon subsequent ventilations if the patient gaspsand locks valve 650 open and inactive.

[0189] Valve 650 is incorporated into a system housing 672 having aninlet end 674 and an outlet end 676. Conveniently, patient ventilationmay occur through inlet end 674 using a ventilatory source similar toother embodiments. Outlet end 676 may be coupled to an interface thatpermits system 670 to be interfaced with the patient's airway. Disposedwithin housing 672 is a one way membrane valve 678 that is spaced apartfrom port 680. In FIG. 38, system 670 is in the resting state where nogasp or ventilation has occurred. When performing CPR, the chest iscompressed and air forced from the patient is permitted to flow throughport 680 and through valve 678. During decompression of the patient'schest, valve membrane 678 moves against port 680 to close the valve asthe negative intrathoracic pressure is increased. If a thresholdpressure is overcome, valve 650 opens to permit respiratory gases toflow through opening 676 after passing through valve 650. Valve 650 thenmoves back to the closed position and the cycle is repeated.

[0190] If valve system 670 is coupled to a patient's airway and thepatient gasps or begins spontaneously breathing, valve system 670automatically adjusts to the configuration shown in FIG. 39 so that thepatient may breathe through a resistance fee airway path so thatrespiratory gas exchange may occur. When the patient gasps or begins tobreathe, valve 678 closes and the negative pressure causes valve 650 toopen and lock in place in a manner similar to that previously describedin connection with FIG. 37. In this way, valve 650 remains open andinactive until reset by the rescuer by pulling on pull tab 668.

[0191] Another way to place valve 650 back into the closed or activeposition is by ventilating the patient through inlet 674 as shown inFIG. 40. When injecting a respiratory gas into inlet 674, the injectedgases flow through valve 678 and through port 680 where the exit throughoutlet 676 and to the patient. In so doing, the flow of gases moves aventilation flap 682 that in turn moves an arm 684 that is coupled to awedge 686. Movement of wedge 686 causes lateral movement of an arm 688that is connected to a reset wedge 690. Wedge 690 rests on top of anupward movement ramp 692. As arm 688 is laterally moved, wedge 690 movesup ramp 692 and contacts pull tab 668. In so doing, valve member 656 ispulled up until pins 662 are pulled from grooves 664 and valve 650 movesback to the closed and active position by force of spring 660. A resetspring 694 then resets ventilation flap 682 back to its home positionand wedge 690 slides back down ramp 692 so that valve 650 may be resetback to the closed position if subsequently needed. Valve 650 remains inthe closed and active position until another gasp or spontaneousbreathing occurs.

[0192]FIG. 41 schematically illustrates another embodiment of a valvingsystem 700 that is configured to display the pressure within thepatient's chest during CPR. Valving system 700 may be configured to besimilar to any of the valving systems described herein. Hence, forconvenience of discussion, valving system 700 will only be brieflydescribed. Valving system 700 comprises a housing 702 having an inlet704 and an outlet 706. A pressure responsive valve 708 is used tocontrol the inflow of gases into housing 702 during decompression of thepatient's chest in a manner similar to that described with otherembodiments. A pressure gauge 710 is provided to measure and display thepressure within housing 702 which corresponds to the pressure within thepatient's chest. In this way, pressure gauge 710 may be used to provideimmediate feedback to the rescuer and may be used as a guide todetermine if chest compressions and/or decompressions are beingappropriately performed.

[0193] A pressure sensing port 712 is connected to a tube 714 that isconnected to a pressure sensing control unit 716. In this manner, achange in pressure may be detected during either chest compressions ordecompressions and act as a counting circuit to trigger ventilationcontrol circuitry 718 to automatically ventilate the patient using aventilator 720 after a certain number have been detected.

[0194] Alternatively, a digital control unit may be used that displaysthe pressure within the chest as well as the number of compressionsbetween ventilations. With such a configuration, pressure sensing port712 transmits pneumatically the pressure information. As such, apressure gauge on housing 702 would not be required.

[0195] The valving systems of the invention may also be used to treatshock. Shock may conveniently be defined as a critically low bloodpressure that, when untreated, may lead to death or disability. Types ofshock that may be treated using techniques of the invention include, butare not limited to, low blood pressure secondary to blood loss, heatstroke, vasovagal syncope (the common faint), drowning, drug overdose,heart attack, right heart failure, return to earth after space flight,sepsis, pericardial effusion, tamponade, and the like. Further, thevalve systems of the invention may be used to alter the carotidcardiopulmonary reflex sensitivity that controls blood pressure (bydecreasing intra thoracic pressures with inspiration).

[0196] The valve system that are employed to treat shock are configuredto completely prevent or provide resistance to the inflow of respiratorygases into the patient while the patient is breathing. For valve systemsthat completely prevent the flow of respiratory gases, such valves maybe configured as pressure responsive valves that open after a thresholdnegative intra thoracic pressure has been reached. Valve systems thatsimply provide resistance to the inflow of respiratory gases may also bevariable so that once a desired negative intra thoracic pressure isreached, the resistance to flow may be lessened. Further, the valves ofthe invention may be configured to be variable, either manually orautomatically. The extent to which the resistance to flow is varied maybe based on physiological parameters measured by one or more sensorsthat are associated with the person being treated. As such, theresistance to flow may be varied so that the person's physiologicalparameters are brought within an acceptable range. Examples ofphysiological parameters that may be measured include, but are notlimited to, negative intra thoracic pressure, respiratory rate, endtidal CO₂, positive end expiratory pressure, blood pressure, oxygensaturation, tissue CO₂ content, and the like. If an automated system isused, such sensors may be coupled to a controller which is employed tocontrol one or more mechanisms that vary the resistance or actuatingpressure of the inflow valve.

[0197] Referring now to FIGS. 42 and 43, one embodiment of a system 800that may be used to treat a person in shock will be described. System800 comprises a housing 802 that is coupled to a facial mask 804.Housing 802 includes an inspiratory fenestrated port 806 where inspiredgases are permitted to enter housing 802. Disposed below port 806 is aslotted airway resistance mechanism 808 that may be used to completelyprevent or provide resistance to the respiratory gases flowing intohousing 802 through port 806. Resistance mechanism 808 is alsoillustrated in FIGS. 46A and 46B and may be constructed of a slottedmember 810 and a slotted plate 812. Slotted member 810 is movablerelative to plate 812 to partially or fully cover the slots in plate 812as illustrated in FIG. 46B. In this way, the resistance to the flow ofinspired gases may be increased simply by moving slotted plate 812relative to slotted member 810. As best shown in FIG. 42, a motor 814that moves a shaft 816 may be employed to translate slotted member 810over slotted plate 812 to vary the resistance to flow. Optionally, afilter 818 may be disposed below resistance mechanism 808.

[0198] System 800 further includes a one-way valve 820 that preventsexpired gases from flowing back up through resistance mechanism 808.Disposed upstream of one-way valve 820 is an oxygen port 822 to permitoxygen to be supplied to the person during inspiration. System 800further includes another one-way valve 824 that opens when the personexpires to permit expired gases from exiting housing 802 through anexpiratory port 826.

[0199] System 800 may also include one or more sensors 828 that measurevarious physiological parameters, such as flow rate, internal pressureswithin the patient, end tidal CO₂, and the like. These sensors may becoupled to a circuit board or controller 830 that may be programmed tovary operation of motor 814 based on the sensed parameters. In this way,the measured parameters may be kept within a desired range simply bycontrolling the resistance provided by resistance mechanism 808 in anautomated manner. Although not shown, it will be appreciated that othersensors may also be coupled to circuit board 830 and may not necessarilybe incorporated into housing 802 or mask 804. System 800 may alsoinclude a battery 832 to provide power to the various electricalcomponents of system 800. A control button 834 may also be employed toactuate system 800.

[0200] Optionally, to ensure that the inspiratory lumen is nevercompletely occluded by the airway resistance mechanisms, molded stopsmay be fabricated in a manner that the airway may always have a slightopening for inspiration to occur. As another option, the valve andsensing system may be attached to other airway devices, including anendo tracheal tube, a laryngeal mask, or the like.

[0201]FIG. 44 illustrates system 800 when mask 804 is coupled to aperson and the person inhales. As shown, the inspired gases pass throughresistance mechanism 808 which has been operated to increase theresistance to flow. Optionally oxygen may also be supplied to the personthrough oxygen port 822. FIG. 45 illustrates when the person exhales. Asshown, the expired gases pass through one-way port 824 and throughexpiratory port 826.

[0202] Although system 800 has been shown with one particular type ofvalve, it will be appreciated that a variety of inflow valves may beused including any of those previously described. Further, FIGS. 47-53illustrate other types of inflow valves that may be used to prevent orincrease the resistance to flow during an inspiratory effort. Further,any of these inflow valves may be coupled to other mechanisms that maybe used to operate the valve to vary the flow resistance. In this way, acontroller may be used to automatically control the amount ofresistance. Further, the controller may be coupled to one or moresensors so that various physiological parameters of the person may bekept within a desired range simply by measuring the parameters and usingthose parameters to vary the amount of resistance.

[0203]FIGS. 47A and 47B illustrate an inflow valve 836 that comprises anairway 838 and a movable disk 840. Disk 840 may be moved by any type ofmechanical mechanism to occlude airway 838 as shown to increase flowresistance.

[0204]FIG. 48A and FIG. 48B illustrate another embodiment of an inflowvalve 842 that comprises an airway 844 and a rotatable disk 846. Asshown in FIG. 48B, disk 846 may be rotated to increase the amount offlow resistance through airway 844.

[0205]FIGS. 49A and 49B illustrate an inflow valve 848 that comprises anairway 850 that is positioned between a pair of plates 852 and 854. Asshown in FIG. 49B, a rotatable cam 856 may be employed to move plate 854to compress airway 850 and thereby increase flow resistance.Conveniently, cam 856 may be rotated by a motor 858 that in turn may becontrolled by a controller in a manner similar to that previouslydescribed.

[0206]FIGS. 50A and 50B illustrate a further embodiment of an inflowvalve 860 that comprises an airway 862 that is positioned between twoplates 864 and 866. In turn, plate 866 is coupled to a threaded shaft868 that is movable back and forth by a stepper motor 870 that may alsobe coupled to a controller. In operation, stepper motor 870 is employedto move plate 866 against airway 862 as shown in FIG. SOB to increasethe resistance to flow.

[0207]FIGS. 51A and 51B illustrate an inflow valve 872 that comprises anairway 874 that is positioned between a pair of plates 876 and 878.These plates are coupled to a caliper mechanism 880 that in turn iscoupled to a lead screw 882 that is movable by a stepper motor 884. Inthis way, stepper motor 884 may be used to operate caliper mechanism 880to in turn squeeze airway 874 as shown in FIG. 51B to increase flowresistance.

[0208]FIGS. 52A and 52B illustrate an inflow valve 886 that comprises aniris occluding mechanism 888. As shown in FIG. 52B, iris occludingmechanism 888 may be operated to decrease the size of the airway andthereby increase flow resistance.

[0209]FIGS. 53A and 53B illustrate another embodiment of an inflow valve890 that comprises an airway 892 and a rotatable arm 894 that in turnmay be coupled to a stepper motor. As shown in FIG. 53B, arm 894 isrotatable over airway 892 to increase resistance to flow.

[0210]FIGS. 54A through 54C illustrate one exemplary method for treatinga person in shock. The process begins at step 900 where the treatmentsystem may be coupled to the patient's airway. For example, the systempreviously described in connection with FIG. 42 may be coupled to thepatient's face. The power is turned on as shown in step 902 and theairway resistance mechanism may be set to an open position as shown instep 904. The treatment mechanism may include various presetphysiological parameters that may initially be read to determine theperson's condition. At step 908, a determination is made as to whether abreath has been sensed based on the physiological parameters previouslyread in step 906. If no breath has been sensed, the process is reversedback to step 904 to ensure that the airway resistance mechanism is inthe open position.

[0211] If a breath has been sensed, the process proceeds to step 910where the airway resistance mechanism is set to a preset position. Thisposition may be based on the initial physiological parameters that weresensed in step 906. Further, the airway resistance may be set manuallyor may be done automatically using a controller that is programmed withvarious preset positions based on measured physiological parameters. Theprocess then proceeds to step 912 where the physiological parameters areevaluated to determine whether the negative inspiratory pressure isacceptable as the patient inhales. If the negative inspiratory pressureis too low, the process proceeds to step 914 where the airway resistanceis increased. This may be done in an automated manner using thecontroller which operates the airway resistance mechanism to increasethe airway resistance. After the resistance has been increased, theprocess proceeds to step 916 where sensors are employed to determinewhether a breath is sensed. If not, the process reverts back to step 904where the airway resistance is moved back to its original position or toa fully open position and the process continues.

[0212] If the negative inspiratory pressure is too high, the process mayproceed to step 918 where airway resistance is reduced. A breathmeasurement is then taken in step 920 to determine whether a breath issensed. If not, the process proceeds back to step 904 where the airwayresistance mechanism may be opened. If a breath is sensed in either step920 or step 916, the process goes back to step 912 where another checkon the negative inspiratory pressure is made. Once the negativeinspiratory pressure is acceptable, the process proceeds to step 922where the respiratory rate is evaluated. If the respiratory rate isunacceptable, the process proceeds to step 924 where the airwayresistance is reduced. An evaluation as to whether a breath is sensed ismade in step 926. If no breath is sensed, the process reverts back tostep 904 where the airway resistance mechanism may be open. If a breathis sensed, the process proceeds back to step 922 where anotherevaluation of the respiratory rate is made. If the respiratory rate isacceptable, the process proceeds to step 928 and an evaluation as to theend tidal CO₂ is made. If too low, airway resistance is increased asshown in step 930 and another evaluation is made as to whether thepatient is breathing in step 932. If not, the process proceeds back tostep 904 where the airway resistance mechanism is opened. If the endtidal CO₂ is too high, the process proceeds to step 934 where the airwayresistance is reduced and the patient's breathing is again sensed atstep 936. If no breath is sensed, the process proceeds back to step 904where the airway resistance mechanism is opened. If a breath is sensedin either steps 932 or 936, the process proceeds back to step 928 wherethe end tidal CO₂ is re-evaluated. Once acceptable, the process proceedsto step 938 where the oxygen saturation is evaluated. If too low, theairway resistance may be decreased as shown in step 940 and anevaluation is made as to whether the person is breathing as shown instep 942. If not, the process proceeds back to step 904 and the airwayresistance mechanism is opened. If the oxygen saturation is acceptable,the process proceeds to step 912 so that the negative inspiratorypressure, respiratory rate, end tidal CO₂, and oxygen saturation may becontinuously monitored and the airway resistance may be modified basedon the parameters.

[0213] Hence, the method set forth in FIGS. 54A through 54C permitsvarious physiological parameters to be continuously monitored and topermit the resistance to inspiratory flow to be modified so that theseparameters remain within an acceptable range when treating a patientsuffering from shock. Further, as previously described, the augmentationof negative inspiratory pressure permits increased blood flow back tothe right heart to increase the patient's blood pressure. Although shownmonitoring the various physiological parameters in a certain order, itwill be appreciated that the parameters may be monitored in other ordersas well. Further, other physiological parameters may be measured toensure that the patient remains in a stable condition when treating thepatient for shock. Optionally, the method of FIGS. 54A through 54C mayalso be used to evaluate the patient's positive end expiratory pressure.Further, similar airway resistance mechanisms may be applied to theexpiratory port and the airway resistance of the expiratory port may bevaried based on the sensed parameters. For example, the expiratorypressure may be varied to aid in the prevention of alveoli collapse(atelectasis) which may occur when the negative intrathoracic pressureis too low for a prolonged period of time.

[0214] Although the foregoing invention has been described in somedetail by way of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

What is claimed is:
 1. A method for increasing circulation in abreathing person, the method comprising: interfacing a valve system tothe person's airway, the valve system being configured to decrease orprevent respiratory gas flow to the person's lungs during at least aportion of an inhalation event; permitting the person to inhale andexhale through the valve system, wherein during inhalation the valvesystem functions to produce a vacuum within the thorax to increase bloodflow back to the right heart of the person, thereby increasing cardiacoutput and blood circulation.
 2. A method as in claim 1, wherein thevalve system is incorporated into a facial mask, and further comprisingcoupling the facial mask to the person's face.
 3. A method as in claim1, wherein the valve system includes a pressure responsive inflow valve,and further comprising setting an actuating pressure of the valve to bein the range from about 0 cm H₂O to about −40 cm H₂O.
 4. A method as inclaim 1, further comprising varying the actuating pressure of the valveover time.
 5. A method as in claim 1, wherein the valve system isfurther configured to prevent or decrease exhaled gases from exiting theperson's lungs during at least a portion of an exhalation event tofurther increase blood circulation.
 6. A method as in claim 1, whereinthe valve system is interfaced for a time period in the range from about30 seconds to about 24 hours.
 7. A method as in claim 1, furthercomprising adding a supply of oxygen through the valve system tosupplement oxygen delivery to the person.
 8. A method as in claim 1,wherein the person is suffering from a disease that is related toimpaired venous blood flow.
 9. A method as in claim 1, wherein theperson is suffering from a disease resulting at least in part from poorblood circulation, and wherein the valve system functions to increaseblood circulation to treat the disease.
 10. A method as in claim 9,wherein the disease is selected from a group consisting of venous stasisulcers, deep vein thrombosis, wound healing, and lymphedema.
 11. Amethod as in claim 9, wherein the disease comprises renal failure.